[PATCH v2 05/29] drm/gpusvm: Add support for GPU Shared Virtual Memory
Matthew Brost
matthew.brost at intel.com
Mon Nov 4 23:07:06 UTC 2024
On Mon, Nov 04, 2024 at 07:59:10PM +0100, Thomas Hellström wrote:
> On Mon, 2024-11-04 at 09:21 -0800, Matthew Brost wrote:
> > On Mon, Nov 04, 2024 at 04:25:38PM +0100, Thomas Hellström wrote:
> > > On Tue, 2024-10-15 at 20:24 -0700, Matthew Brost wrote:
> > >
> > > Continued review.
> > >
> > > >
> > > > +/**
> > > > + * struct drm_gpusvm_zdd - GPU SVM zone device data
> > > > + *
> > > > + * @refcount: Reference count for the zdd
> > > > + * @destroy_work: Work structure for asynchronous zdd
> > > > destruction
> > > > + * @devmem_allocation: device memory allocation
> > > > + * @device_private_page_owner: Device private pages owner
> > > > + *
> > > > + * This structure serves as a generic wrapper installed in
> > > > + * page->zone_device_data. It provides infrastructure for
> > > > looking up
> > > > a device
> > > > + * memory allocation upon CPU page fault and asynchronously
> > > > releasing device
> > > > + * memory once the CPU has no page references. Asynchronous
> > > > release
> > > > is useful
> > > > + * because CPU page references can be dropped in IRQ contexts,
> > > > while
> > > > releasing
> > > > + * device memory likely requires sleeping locks.
> > > > + */
> > > > +struct drm_gpusvm_zdd {
> > > > + struct kref refcount;
> > > > + struct work_struct destroy_work;
> > > > + struct drm_gpusvm_devmem *devmem_allocation;
> > > > + void *device_private_page_owner;
> > > > +};
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_zdd_destroy_work_func - Work function for
> > > > destroying a
> > > > zdd
> > >
> > > NIT: Even if the above kerneldoc format works, I keep trying to
> > > enforce
> > > using () after function names and function-like macros, like
> > > described
> > > here: https://docs.kernel.org/doc-guide/kernel-doc.html Could we
> > > update? Also that doc calls for using "Return:" instead of
> > > "Returns:".
> > >
> > >
> >
> > Will fix up. Thanks for the ref.
> >
> > > > + * @w: Pointer to the work_struct
> > > > + *
> > > > + * This function releases device memory, puts GPU SVM range, and
> > > > frees zdd.
> > > > + */
> > > > +static void drm_gpusvm_zdd_destroy_work_func(struct work_struct
> > > > *w)
> > > > +{
> > > > + struct drm_gpusvm_zdd *zdd =
> > > > + container_of(w, struct drm_gpusvm_zdd,
> > > > destroy_work);
> > > > + const struct drm_gpusvm_devmem_ops *ops = zdd-
> > > > > devmem_allocation ?
> > > > + zdd->devmem_allocation->ops : NULL;
> > > > +
> > > > + if (zdd->devmem_allocation && ops->devmem_release)
> > > > + ops->devmem_release(zdd->devmem_allocation);
> > > > + kfree(zdd);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_zdd_alloc - Allocate a zdd structure.
> > > > + * @device_private_page_owner: Device private pages owner
> > > > + *
> > > > + * This function allocates and initializes a new zdd structure.
> > > > It
> > > > sets up the
> > > > + * reference count and initializes the destroy work.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the allocated zdd on success, ERR_PTR() on
> > > > failure.
> > > > + */
> > > > +static struct drm_gpusvm_zdd *
> > > > +drm_gpusvm_zdd_alloc(void *device_private_page_owner)
> > > > +{
> > > > + struct drm_gpusvm_zdd *zdd;
> > > > +
> > > > + zdd = kmalloc(sizeof(*zdd), GFP_KERNEL);
> > > > + if (!zdd)
> > > > + return NULL;
> > > > +
> > > > + kref_init(&zdd->refcount);
> > > > + INIT_WORK(&zdd->destroy_work,
> > > > drm_gpusvm_zdd_destroy_work_func);
> > > > + zdd->devmem_allocation = NULL;
> > > > + zdd->device_private_page_owner =
> > > > device_private_page_owner;
> > > > +
> > > > + return zdd;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_zdd_get - Get a reference to a zdd structure.
> > > > + * @zdd: Pointer to the zdd structure.
> > > > + *
> > > > + * This function increments the reference count of the provided
> > > > zdd
> > > > structure.
> > > > + *
> > > > + * Returns: Pointer to the zdd structure.
> > > > + */
> > > > +static struct drm_gpusvm_zdd *drm_gpusvm_zdd_get(struct
> > > > drm_gpusvm_zdd *zdd)
> > > > +{
> > > > + kref_get(&zdd->refcount);
> > > > + return zdd;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_zdd_destroy - Destroy a zdd structure.
> > > > + * @ref: Pointer to the reference count structure.
> > > > + *
> > > > + * This function queues the destroy_work of the zdd for
> > > > asynchronous
> > > > destruction.
> > > > + */
> > > > +static void drm_gpusvm_zdd_destroy(struct kref *ref)
> > > > +{
> > > > + struct drm_gpusvm_zdd *zdd =
> > > > + container_of(ref, struct drm_gpusvm_zdd,
> > > > refcount);
> > > > +
> > > > + if (zdd->devmem_allocation)
> > > > + WRITE_ONCE(zdd->devmem_allocation->detached,
> > > > true);
> > > > + schedule_work(&zdd->destroy_work);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_zdd_put - Put a zdd reference.
> > > > + * @zdd: Pointer to the zdd structure.
> > > > + *
> > > > + * This function decrements the reference count of the provided
> > > > zdd
> > > > structure
> > > > + * and schedules its destruction if the count drops to zero.
> > > > + */
> > > > +static void drm_gpusvm_zdd_put(struct drm_gpusvm_zdd *zdd)
> > > > +{
> > > > + kref_put(&zdd->refcount, drm_gpusvm_zdd_destroy);
> > > > +}
> > >
> > > As mentioned earlier, I think the above drm_gpusvm_zdd functions
> > > should
> > > move to drm_pagemap.c. I don't think they are used in drm_gpusvm
> > > other
> > > than to, at get_pages time, ensure all device private pages are
> > > from
> > > the same pagemap?
> > >
> >
> > The are used in __drm_gpusvm_migrate_to_ram to find devmem_allocation
> > and
> > associated ops.
> >
> > Also in drm_gpusvm_migrate_to_ram to find the size and
> > device_private_page_owner.
> >
> > I think the placement here is correct for now but open to shuffling
> > this around
> > in the future if this makes sense.
>
> Yeah I was thinking with the split in the multi-device series, (which
> is yet to be posted, though, the drm_pagemap op (*populate_mm)() would
> in effect handle all migration to vram, and the dev_pagemap op would
> handle migration to ram, and the ranges would no longer keep track of
> the vram allocations.
>
I'd have to look at the multi-device stuff to fully understand this.
> This means that no low-level migration function would take drm_gpusvm
> as an argument (well drm_gpusvm_range_evict() would, but that would, as
> we discussed before probably want to evict *all* device private pages,
> so that it would likely need to be implemented with hmm_range_fault()?
>
hmm_range_fault doesn't work when trying to evict coherent pages... otherwise
yea that would be an easy to implement drm_gpusvm_range_evict. At one point had
it that way.
> So this was mostly trying to avoid future shuffling around, but agree
> it depends on dev_pagemap patches.
>
Churn isn't great but I think it bound to happen as we implement more things /
do perf optimizations in Xe on top this series. I think I'm ok with that as long
it is more or less just moving code around, not large rewrites.
> >
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_find - Find GPU SVM range from GPU SVM
> > > > notifier
> > > > + * @notifier: Pointer to the GPU SVM notifier structure.
> > > > + * @start: Start address of the range
> > > > + * @end: End address of the range
> > > > + *
> > > > + * Return: A pointer to the drm_gpusvm_range if found or NULL
> > > > + */
> > > > +struct drm_gpusvm_range *
> > > > +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, u64
> > > > start, u64 end)
> > > > +{
> > > > + return range_iter_first(¬ifier->root, start, end -
> > > > 1);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_for_each_range_safe - Safely iterate over GPU SVM
> > > > ranges in a notifier
> > > > + * @range__: Iterator variable for the ranges
> > > > + * @next__: Iterator variable for the ranges temporay storage
> > > > + * @notifier__: Pointer to the GPU SVM notifier
> > > > + * @start__: Start address of the range
> > > > + * @end__: End address of the range
> > > > + *
> > > > + * This macro is used to iterate over GPU SVM ranges in a
> > > > notifier
> > > > while
> > > > + * removing ranges from it.
> > > > + */
> > > > +#define drm_gpusvm_for_each_range_safe(range__, next__,
> > > > notifier__,
> > > > start__, end__) \
> > > > + for ((range__) = drm_gpusvm_range_find((notifier__),
> > > > (start__), (end__)), \
> > > > + (next__) =
> > > > __drm_gpusvm_range_next(range__); \
> > > > + (range__) && (range__->va.start <
> > > > (end__)); \
> > > > + (range__) = (next__), (next__) =
> > > > __drm_gpusvm_range_next(range__))
> > > > +
> > > > +/**
> > > > + * __drm_gpusvm_notifier_next - get the next drm_gpusvm_notifier
> > > > in
> > > > the list
> > > > + * @notifier: a pointer to the current drm_gpusvm_notifier
> > > > + *
> > > > + * Return: A pointer to the next drm_gpusvm_notifier if
> > > > available,
> > > > or NULL if
> > > > + * the current notifier is the last one or if the input
> > > > notifier is
> > > > + * NULL.
> > > > + */
> > > > +static struct drm_gpusvm_notifier *
> > > > +__drm_gpusvm_notifier_next(struct drm_gpusvm_notifier *notifier)
> > > > +{
> > > > + if (notifier && !list_is_last(¬ifier->rb.entry,
> > > > + ¬ifier->gpusvm-
> > > > > notifier_list))
> > > > + return list_next_entry(notifier, rb.entry);
> > >
> > > Why aren't we using notifier_iter_next() here? Then the linked list
> > > could be skipped.
> > >
> >
> > I shamlessly copied this from GPU VM. I think the list is useful for
> > faster
> > iteration and safe removal of items while walking.
>
> We
> havehttps://elixir.bootlin.com/linux/v6.12-rc6/source/include/linux/interval_tree_generic.h#L24
>
> to relate to. Now GPUVM can't use the generic version since it needs
> u64 intervals. These trees need unsigned long only so it should be ok.
> And safe removal, isn't that possible to implement without the list?
> Then it's really only the linked list as a perf optimization I guess,
> but we have a lot of those pending...
>
See my other comments. Let me just follow on using a maple tree and perhaps a
list isn't required if we use that. Will have definite answer in my next rev.
>
>
> >
> > > > +
> > > > + return NULL;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_for_each_notifier - Iterate over GPU SVM notifiers
> > > > in
> > > > a gpusvm
> > > > + * @notifier__: Iterator variable for the notifiers
> > > > + * @notifier__: Pointer to the GPU SVM notifier
> > > > + * @start__: Start address of the notifier
> > > > + * @end__: End address of the notifier
> > > > + *
> > > > + * This macro is used to iterate over GPU SVM notifiers in a
> > > > gpusvm.
> > > > + */
> > > > +#define drm_gpusvm_for_each_notifier(notifier__, gpusvm__,
> > > > start__,
> > > > end__) \
> > > > + for ((notifier__) = notifier_iter_first(&(gpusvm__)-
> > > > >root,
> > > > (start__), (end__) - 1); \
> > > > + (notifier__) && (notifier__->interval.start <
> > > > (end__)); \
> > > > + (notifier__) =
> > > > __drm_gpusvm_notifier_next(notifier__))
> > > > +
> > >
> > > Looks like end__ is not honored except for the first iteration.
> > > Relates
> > > to the above question.
> > >
> >
> > Again shameless copy from GPU VM... Missing what the problem is. The
> > condition
> > to break the loop is:
> >
> > '(notifier__) && (notifier__->interval.start < (end__)'
>
> Ah yes, you're right. I missed that.
>
> >
> > > > +/**
> > > > + * drm_gpusvm_for_each_notifier_safe - Safely iterate over GPU
> > > > SVM
> > > > notifiers in a gpusvm
> > > > + * @notifier__: Iterator variable for the notifiers
> > > > + * @next__: Iterator variable for the notifiers temporay storage
> > > > + * @notifier__: Pointer to the GPU SVM notifier
> > > > + * @start__: Start address of the notifier
> > > > + * @end__: End address of the notifier
> > > > + *
> > > > + * This macro is used to iterate over GPU SVM notifiers in a
> > > > gpusvm
> > > > while
> > > > + * removing notifiers from it.
> > > > + */
> > > > +#define drm_gpusvm_for_each_notifier_safe(notifier__, next__,
> > > > gpusvm__, start__, end__) \
> > > > + for ((notifier__) = notifier_iter_first(&(gpusvm__)-
> > > > >root,
> > > > (start__), (end__) - 1), \
> > > > + (next__) =
> > > > __drm_gpusvm_notifier_next(notifier__); \
> > > > + (notifier__) && (notifier__->interval.start <
> > > > (end__)); \
> > > > + (notifier__) = (next__), (next__) =
> > > > __drm_gpusvm_notifier_next(notifier__))
> > >
> > > Same here.
> > >
> >
> > Alsp present:
> >
> > (notifier__) && (notifier__->interval.start < (end__)
> >
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_invalidate - Invalidate a GPU SVM
> > > > notifier.
> > > > + * @mni: Pointer to the mmu_interval_notifier structure.
> > > > + * @mmu_range: Pointer to the mmu_notifier_range structure.
> > > > + * @cur_seq: Current sequence number.
> > > > + *
> > > > + * This function serves as a generic MMU notifier for GPU SVM.
> > > > It
> > > > sets the MMU
> > > > + * notifier sequence number and calls the driver invalidate
> > > > vfunc
> > > > under
> > > > + * gpusvm->notifier_lock.
> > > > + *
> > > > + * Returns:
> > > > + * true if the operation succeeds, false otherwise.
> > > > + */
> > > > +static bool
> > > > +drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier
> > > > *mni,
> > > > + const struct mmu_notifier_range
> > > > *mmu_range,
> > > > + unsigned long cur_seq)
> > > > +{
> > > > + struct drm_gpusvm_notifier *notifier =
> > > > + container_of(mni, typeof(*notifier), notifier);
> > > > + struct drm_gpusvm *gpusvm = notifier->gpusvm;
> > > > +
> > > > + if (!mmu_notifier_range_blockable(mmu_range))
> > > > + return false;
> > > > +
> > > > + down_write(&gpusvm->notifier_lock);
> > > > + mmu_interval_set_seq(mni, cur_seq);
> > > > + gpusvm->ops->invalidate(gpusvm, notifier, mmu_range);
> > > > + up_write(&gpusvm->notifier_lock);
> > > > +
> > > > + return true;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_ops - MMU interval notifier operations
> > > > for
> > > > GPU SVM
> > > > + */
> > > > +static const struct mmu_interval_notifier_ops
> > > > drm_gpusvm_notifier_ops = {
> > > > + .invalidate = drm_gpusvm_notifier_invalidate,
> > > > +};
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_init - Initialize the GPU SVM.
> > > > + * @gpusvm: Pointer to the GPU SVM structure.
> > > > + * @name: Name of the GPU SVM.
> > > > + * @drm: Pointer to the DRM device structure.
> > > > + * @mm: Pointer to the mm_struct for the address space.
> > > > + * @device_private_page_owner: Device private pages owner.
> > > > + * @mm_start: Start address of GPU SVM.
> > > > + * @mm_range: Range of the GPU SVM.
> > > > + * @notifier_size: Size of individual notifiers.
> > > > + * @ops: Pointer to the operations structure for GPU SVM.
> > > > + * @chunk_sizes: Pointer to the array of chunk sizes used in
> > > > range
> > > > allocation.
> > > > + * Entries should be powers of 2 in descending
> > > > order
> > > > with last
> > > > + * entry being SZ_4K.
> > > > + * @num_chunks: Number of chunks.
> > > > + *
> > > > + * This function initializes the GPU SVM.
> > > > + *
> > > > + * Returns:
> > > > + * 0 on success, a negative error code on failure.
> > > > + */
> > > > +int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> > > > + const char *name, struct drm_device *drm,
> > > > + struct mm_struct *mm, void
> > > > *device_private_page_owner,
> > > > + u64 mm_start, u64 mm_range, u64
> > > > notifier_size,
> > > > + const struct drm_gpusvm_ops *ops,
> > > > + const u64 *chunk_sizes, int num_chunks)
> > > > +{
> > > > + if (!ops->invalidate || !num_chunks)
> > > > + return -EINVAL;
> > > > +
> > > > + gpusvm->name = name;
> > > > + gpusvm->drm = drm;
> > > > + gpusvm->mm = mm;
> > > > + gpusvm->device_private_page_owner =
> > > > device_private_page_owner;
> > > > + gpusvm->mm_start = mm_start;
> > > > + gpusvm->mm_range = mm_range;
> > > > + gpusvm->notifier_size = notifier_size;
> > > > + gpusvm->ops = ops;
> > > > + gpusvm->chunk_sizes = chunk_sizes;
> > > > + gpusvm->num_chunks = num_chunks;
> > > > +
> > > > + mmgrab(mm);
> > > > + gpusvm->root = RB_ROOT_CACHED;
> > > > + INIT_LIST_HEAD(&gpusvm->notifier_list);
> > > > +
> > > > + init_rwsem(&gpusvm->notifier_lock);
> > > > +
> > > > + fs_reclaim_acquire(GFP_KERNEL);
> > > > + might_lock(&gpusvm->notifier_lock);
> > > > + fs_reclaim_release(GFP_KERNEL);
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_find - Find GPU SVM notifier
> > > > + * @gpusvm__: Pointer to the GPU SVM structure
> > > > + * @fault_addr__: Fault address
> > > > + *
> > > > + * This macro finds the GPU SVM notifier associated with the
> > > > fault
> > > > address.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the GPU SVM notifier on success, NULL otherwise.
> > > > + */
> > > > +#define drm_gpusvm_notifier_find(gpusvm__,
> > > > fault_addr__) \
> > > > + notifier_iter_first(&(gpusvm__)->root,
> > > > (fault_addr__), \
> > > > + (fault_addr__ + 1))
> > > > +
> > > > +/**
> > > > + * to_drm_gpusvm_notifier - retrieve the container struct for a
> > > > given rbtree node
> > > > + * @node__: a pointer to the rbtree node embedded within a
> > > > drm_gpusvm_notifier struct
> > > > + *
> > > > + * Return: A pointer to the containing drm_gpusvm_notifier
> > > > structure.
> > > > + */
> > > > +#define
> > > > to_drm_gpusvm_notifier(__node) \
> > > > + container_of((__node), struct drm_gpusvm_notifier,
> > > > rb.node)
> > > > +
> > >
> > > There appears to be a number of function-like macros in the code,
> > > which
> > > look like they can be converted to functions. Linux prefers
> > > functions
> > > over macros when possible:
> > >
> > > https://www.kernel.org/doc/html/v5.8/process/coding-style.html#macros-enums-and-rtl
> > >
> >
> > Will convert all macros to functions if possible. Again thanks for
> > ref.
> >
> > >
> > > > +/**
> > > > + * drm_gpusvm_notifier_insert - Insert GPU SVM notifier
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + *
> > > > + * This function inserts the GPU SVM notifier into the GPU SVM
> > > > RB
> > > > tree and list.
> > > > + */
> > > > +static void drm_gpusvm_notifier_insert(struct drm_gpusvm
> > > > *gpusvm,
> > > > + struct
> > > > drm_gpusvm_notifier
> > > > *notifier)
> > > > +{
> > > > + struct rb_node *node;
> > > > + struct list_head *head;
> > > > +
> > > > + notifier_insert(notifier, &gpusvm->root);
> > > > +
> > > > + node = rb_prev(¬ifier->rb.node);
> > > > + if (node)
> > > > + head = &(to_drm_gpusvm_notifier(node))-
> > > > >rb.entry;
> > > > + else
> > > > + head = &gpusvm->notifier_list;
> > > > +
> > > > + list_add(¬ifier->rb.entry, head);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_remove - Remove GPU SVM notifier
> > > > + * @gpusvm__: Pointer to the GPU SVM tructure
> > > > + * @notifier__: Pointer to the GPU SVM notifier structure
> > > > + *
> > > > + * This macro removes the GPU SVM notifier from the GPU SVM RB
> > > > tree
> > > > and list.
> > > > + */
> > > > +#define drm_gpusvm_notifier_remove(gpusvm__,
> > > > notifier__) \
> > > > + notifier_remove((notifier__), &(gpusvm__)-
> > > > >root); \
> > > > + list_del(&(notifier__)->rb.entry)
> > >
> > > Unless this can be made a function, Pls use
> > > do { } while (0)
> > >
> >
> > I think it can be made a function or otherwise yea will use do { }
> > while (0).
> >
> > >
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_fini - Finalize the GPU SVM.
> > > > + * @gpusvm: Pointer to the GPU SVM structure.
> > > > + *
> > > > + * This function finalizes the GPU SVM by cleaning up any
> > > > remaining
> > > > ranges and
> > > > + * notifiers, and dropping a reference to struct MM.
> > > > + */
> > > > +void drm_gpusvm_fini(struct drm_gpusvm *gpusvm)
> > > > +{
> > > > + struct drm_gpusvm_notifier *notifier, *next;
> > > > +
> > > > + drm_gpusvm_for_each_notifier_safe(notifier, next,
> > > > gpusvm, 0,
> > > > LONG_MAX) {
> > > > + struct drm_gpusvm_range *range, *__next;
> > > > +
> > > > + /*
> > > > + * Remove notifier first to avoid racing with
> > > > any
> > > > invalidation
> > > > + */
> > > > + mmu_interval_notifier_remove(¬ifier-
> > > > >notifier);
> > > > + notifier->flags.removed = true;
> > > > +
> > > > + drm_gpusvm_for_each_range_safe(range, __next,
> > > > notifier, 0,
> > > > + LONG_MAX)
> > > > + drm_gpusvm_range_remove(gpusvm, range);
> > > > + }
> > > > +
> > > > + mmdrop(gpusvm->mm);
> > > > + WARN_ON(!RB_EMPTY_ROOT(&gpusvm->root.rb_root));
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_alloc - Allocate GPU SVM notifier
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @fault_addr: Fault address
> > > > + *
> > > > + * This function allocates and initializes the GPU SVM notifier
> > > > structure.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the allocated GPU SVM notifier on success,
> > > > ERR_PTR()
> > > > on failure.
> > > > + */
> > > > +static struct drm_gpusvm_notifier *
> > > > +drm_gpusvm_notifier_alloc(struct drm_gpusvm *gpusvm, u64
> > > > fault_addr)
> > > > +{
> > > > + struct drm_gpusvm_notifier *notifier;
> > > > +
> > > > + if (gpusvm->ops->notifier_alloc)
> > > > + notifier = gpusvm->ops->notifier_alloc();
> > > > + else
> > > > + notifier = kzalloc(sizeof(*notifier),
> > > > GFP_KERNEL);
> > > > +
> > > > + if (!notifier)
> > > > + return ERR_PTR(-ENOMEM);
> > > > +
> > > > + notifier->gpusvm = gpusvm;
> > > > + notifier->interval.start = ALIGN_DOWN(fault_addr,
> > > > gpusvm-
> > > > > notifier_size);
> > > > + notifier->interval.end = ALIGN(fault_addr + 1, gpusvm-
> > > > > notifier_size);
> > > > + INIT_LIST_HEAD(¬ifier->rb.entry);
> > > > + notifier->root = RB_ROOT_CACHED;
> > > > + INIT_LIST_HEAD(¬ifier->range_list);
> > > > +
> > > > + return notifier;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_notifier_free - Free GPU SVM notifier
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + *
> > > > + * This function frees the GPU SVM notifier structure.
> > > > + */
> > > > +static void drm_gpusvm_notifier_free(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_notifier
> > > > *notifier)
> > > > +{
> > > > + WARN_ON(!RB_EMPTY_ROOT(¬ifier->root.rb_root));
> > > > +
> > > > + if (gpusvm->ops->notifier_free)
> > > > + gpusvm->ops->notifier_free(notifier);
> > > > + else
> > > > + kfree(notifier);
> > > > +}
> > > > +
> > > > +/**
> > > > + * to_drm_gpusvm_range - retrieve the container struct for a
> > > > given
> > > > rbtree node
> > > > + * @node__: a pointer to the rbtree node embedded within a
> > > > drm_gpusvm_range struct
> > > > + *
> > > > + * Return: A pointer to the containing drm_gpusvm_range
> > > > structure.
> > > > + */
> > > > +#define to_drm_gpusvm_range(node__) \
> > > > + container_of((node__), struct drm_gpusvm_range, rb.node)
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_insert - Insert GPU SVM range
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + *
> > > > + * This function inserts the GPU SVM range into the notifier RB
> > > > tree
> > > > and list.
> > > > + */
> > > > +static void drm_gpusvm_range_insert(struct drm_gpusvm_notifier
> > > > *notifier,
> > > > + struct drm_gpusvm_range
> > > > *range)
> > > > +{
> > > > + struct rb_node *node;
> > > > + struct list_head *head;
> > > > +
> > > > + drm_gpusvm_notifier_lock(notifier->gpusvm);
> > > > + range_insert(range, ¬ifier->root);
> > > > +
> > > > + node = rb_prev(&range->rb.node);
> > > > + if (node)
> > > > + head = &(to_drm_gpusvm_range(node))->rb.entry;
> > > > + else
> > > > + head = ¬ifier->range_list;
> > > > +
> > > > + list_add(&range->rb.entry, head);
> > > > + drm_gpusvm_notifier_unlock(notifier->gpusvm);
> > > > +}
> > > > +
> > > > +/**
> > > > + * __drm_gpusvm_range_remove - Remove GPU SVM range
> > > > + * @notifier__: Pointer to the GPU SVM notifier structure
> > > > + * @range__: Pointer to the GPU SVM range structure
> > > > + *
> > > > + * This macro removes the GPU SVM range from the notifier RB
> > > > tree
> > > > and list.
> > > > + */
> > > > +#define __drm_gpusvm_range_remove(notifier__,
> > > > range__) \
> > > > + range_remove((range__), &(notifier__)-
> > > > >root); \
> > > > + list_del(&(range__)->rb.entry)
> > >
> > > Same thing as for the notifier rb tree. And do we need the linked
> > > list?
> > >
> >
> > Same answer.
> >
> > >
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_alloc - Allocate GPU SVM range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + * @fault_addr: Fault address
> > > > + * @chunk_size: Chunk size
> > > > + * @migrate_devmem: Flag indicating whether to migrate device
> > > > memory
> > > > + *
> > > > + * This function allocates and initializes the GPU SVM range
> > > > structure.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the allocated GPU SVM range on success, ERR_PTR()
> > > > on
> > > > failure.
> > > > + */
> > > > +static struct drm_gpusvm_range *
> > > > +drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_notifier *notifier,
> > > > + u64 fault_addr, u64 chunk_size, bool
> > > > migrate_devmem)
> > > > +{
> > > > + struct drm_gpusvm_range *range;
> > > > +
> > > > + if (gpusvm->ops->range_alloc)
> > > > + range = gpusvm->ops->range_alloc(gpusvm);
> > > > + else
> > > > + range = kzalloc(sizeof(*range), GFP_KERNEL);
> > > > +
> > > > + if (!range)
> > > > + return ERR_PTR(-ENOMEM);
> > > > +
> > > > + kref_init(&range->refcount);
> > > > + range->gpusvm = gpusvm;
> > > > + range->notifier = notifier;
> > > > + range->va.start = ALIGN_DOWN(fault_addr, chunk_size);
> > > > + range->va.end = ALIGN(fault_addr + 1, chunk_size);
> > > > + INIT_LIST_HEAD(&range->rb.entry);
> > > > + range->notifier_seq = LONG_MAX;
> > > > + range->flags.migrate_devmem = migrate_devmem ? 1 : 0;
> > > > +
> > > > + return range;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_check_pages - Check pages
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + * @start: Start address
> > > > + * @end: End address
> > > > + *
> > > > + * Check if pages between start and end have been faulted in on
> > > > the
> > > > CPU. Use to
> > > > + * prevent migration of pages without CPU backing store.
> > > > + *
> > > > + * Returns:
> > > > + * True if pages have been faulted into CPU, False otherwise
> > > > + */
> > > > +static bool drm_gpusvm_check_pages(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_notifier
> > > > *notifier,
> > > > + u64 start, u64 end)
> > > > +{
> > > > + struct hmm_range hmm_range = {
> > > > + .default_flags = 0,
> > > > + .notifier = ¬ifier->notifier,
> > > > + .start = start,
> > > > + .end = end,
> > > > + .dev_private_owner = gpusvm-
> > > > > device_private_page_owner,
> > > > + };
> > > > + unsigned long timeout =
> > > > + jiffies +
> > > > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > > > + unsigned long *pfns;
> > > > + unsigned long npages = npages_in_range(start, end);
> > > > + int err, i;
> > > > +
> > > > + mmap_assert_locked(gpusvm->mm);
> > > > +
> > > > + pfns = kvmalloc_array(npages, sizeof(*pfns),
> > > > GFP_KERNEL);
> > > > + if (!pfns)
> > > > + return false;
> > > > +
> > > > + hmm_range.notifier_seq =
> > > > mmu_interval_read_begin(¬ifier-
> > > > > notifier);
> > > > + hmm_range.hmm_pfns = pfns;
> > > > +
> > > > + while (true) {
> > > > + err = hmm_range_fault(&hmm_range);
> > > > + if (err == -EBUSY) {
> > > > + if (time_after(jiffies, timeout))
> > > > + break;
> > > > +
> > > > + hmm_range.notifier_seq =
> > > > mmu_interval_read_begin(¬ifier->notifier);
> > > > + continue;
> > > > + }
> > > > + break;
> > > > + }
> > > > + if (err)
> > > > + goto err_free;
> > > > +
> > > > + for (i = 0; i < npages;) {
> > > > + if (!(pfns[i] & HMM_PFN_VALID)) {
> > > > + err = -EFAULT;
> > > > + goto err_free;
> > > > + }
> > > > + i += 0x1 << hmm_pfn_to_map_order(pfns[i]);
> > > > + }
> > > > +
> > > > +err_free:
> > > > + kvfree(pfns);
> > > > + return err ? false : true;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_chunk_size - Determine chunk size for GPU
> > > > SVM
> > > > range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > > + * @vas: Pointer to the virtual memory area structure
> > > > + * @fault_addr: Fault address
> > > > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > > > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > > > + * @check_pages: Flag indicating whether to check pages
> > > > + *
> > > > + * This function determines the chunk size for the GPU SVM range
> > > > based on the
> > > > + * fault address, GPU SVM chunk sizes, existing GPU SVM ranges,
> > > > and
> > > > the virtual
> > > > + * memory area boundaries.
> > > > + *
> > > > + * Returns:
> > > > + * Chunk size on success, LONG_MAX on failure.
> > > > + */
> > > > +static u64 drm_gpusvm_range_chunk_size(struct drm_gpusvm
> > > > *gpusvm,
> > > > + struct
> > > > drm_gpusvm_notifier
> > > > *notifier,
> > > > + struct vm_area_struct
> > > > *vas,
> > > > + u64 fault_addr, u64
> > > > gpuva_start,
> > > > + u64 gpuva_end, bool
> > > > check_pages)
> > > > +{
> > > > + u64 start, end;
> > > > + int i = 0;
> > > > +
> > > > +retry:
> > > > + for (; i < gpusvm->num_chunks; ++i) {
> > > > + start = ALIGN_DOWN(fault_addr, gpusvm-
> > > > > chunk_sizes[i]);
> > > > + end = ALIGN(fault_addr + 1, gpusvm-
> > > > >chunk_sizes[i]);
> > > > +
> > > > + if (start >= vas->vm_start && end <= vas->vm_end
> > > > &&
> > > > + start >= notifier->interval.start &&
> > > > + end <= notifier->interval.end &&
> > > > + start >= gpuva_start && end <= gpuva_end)
> > > > + break;
> > > > + }
> > > > +
> > > > + if (i == gpusvm->num_chunks)
> > > > + return LONG_MAX;
> > > > +
> > > > + /*
> > > > + * If allocation more than page, ensure not to overlap
> > > > with
> > > > existing
> > > > + * ranges.
> > > > + */
> > > > + if (end - start != SZ_4K) {
> > > > + struct drm_gpusvm_range *range;
> > > > +
> > > > + range = drm_gpusvm_range_find(notifier, start,
> > > > end);
> > > > + if (range) {
> > > > + ++i;
> > > > + goto retry;
> > > > + }
> > > > +
> > > > + /*
> > > > + * XXX: Only create range on pages CPU has
> > > > faulted
> > > > in. Without
> > > > + * this check, or prefault, on BMG
> > > > 'xe_exec_system_allocator --r
> > > > + * process-many-malloc' fails. In the failure
> > > > case,
> > > > each process
> > > > + * mallocs 16k but the CPU VMA is ~128k which
> > > > results in 64k SVM
> > > > + * ranges. When migrating the SVM ranges, some
> > > > processes fail in
> > > > + * drm_gpusvm_migrate_to_devmem with
> > > > 'migrate.cpages
> > > > != npages'
> > > > + * and then upon drm_gpusvm_range_get_pages
> > > > device
> > > > pages from
> > > > + * other processes are collected + faulted in
> > > > which
> > > > creates all
> > > > + * sorts of problems. Unsure exactly how this
> > > > happening, also
> > > > + * problem goes away if
> > > > 'xe_exec_system_allocator --
> > > > r
> > > > + * process-many-malloc' mallocs at least 64k at
> > > > a
> > > > time.
> > > > + */
> > >
> > > Needs to be figured out. I think even in the system allocator case,
> > > if
> > > a user uses malloc() to allocate a GPU only buffer we'd need to
> > > support
> > > that?
> > >
> >
> > I'm not understanding this comment but I do agree what is going on
> > here needs to
> > be figured out.
>
> What I meant was let's say the user mallocs a big buffer to be used by
> the gpu only, and hence should ideally be in device memory, but it's
> never faulted by the CPU. I guess my question should be reformulated,
> what would happen then? Wouldn't it remain in system ram forever?
>
Right now I think we'd fault in 1 CPU page at time, yea not great. See below
will follow on this to get a definite explaination of what is going on here.
> >
> > This comment is actually a bit stale - I think the above test case
> > will pass now
> > if ctx.check_pages is false with a retry loop triggered in GPU fault
> > handler
> > because of mixed pages. However it does appear the test case still
> > finds device
> > pages in hmm_range_fault mapped into a different process which I
> > think should be
> > impossible. Wondering if there is hmm / mm core bug here my test case
> > hits? Let
> > me page this information back and dig in here to see if I can explain
> > what is
> > going on better. Will take sometime but should be able to focus on
> > this during
> > the week
> >
> > Also I think leaving in the check_pages option is a good thing. A
> > call then can
> > choose between 2 things:
> >
> > 1. Only create GPU mappings for CPU pages faulted in (ctx.check_pages
> > = true)
> > 2. create GPU mappings for a VMA and fault in CPU pages
> > (ctx.check_pages =
> > false)
> >
> > If we support 2, then I think xe_svm_copy needs to be updated to
> > clear VRAM for
> > pages which the CPU has not faulted in.
> >
> > >
> > > > + if (check_pages &&
> > > > + !drm_gpusvm_check_pages(gpusvm, notifier,
> > > > start,
> > > > end)) {
> > > > + ++i;
> > > > + goto retry;
> > > > + }
> > > > + }
> > > > +
> > > > + return end - start;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_find_or_insert - Find or insert GPU SVM
> > > > range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @fault_addr: Fault address
> > > > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > > > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > > > + * @ctx: GPU SVM context
> > > > + *
> > > > + * This function finds or inserts a newly allocated a GPU SVM
> > > > range
> > > > based on the
> > > > + * fault address. Caller must hold a lock to protect range
> > > > lookup
> > > > and insertion.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the GPU SVM range on success, ERR_PTR() on
> > > > failure.
> > > > + */
> > > > +struct drm_gpusvm_range *
> > > > +drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm, u64
> > > > fault_addr,
> > > > + u64 gpuva_start, u64 gpuva_end,
> > > > + const struct drm_gpusvm_ctx
> > > > *ctx)
> > > > +{
> > > > + struct drm_gpusvm_notifier *notifier;
> > > > + struct drm_gpusvm_range *range;
> > > > + struct mm_struct *mm = gpusvm->mm;
> > > > + struct vm_area_struct *vas;
> > > > + bool notifier_alloc = false;
> > > > + u64 chunk_size;
> > > > + int err;
> > > > + bool migrate_devmem;
> > > > +
> > > > + if (fault_addr < gpusvm->mm_start ||
> > > > + fault_addr > gpusvm->mm_start + gpusvm->mm_range) {
> > >
> > > return ERR_PTR(-EINVAL)?
> > >
> >
> > Sure.
> >
> > > > + err = -EINVAL;
> > > > + goto err_out;
> > > > + }
> > > > +
> > > > + if (!mmget_not_zero(mm)) {
> > > > + err = -EFAULT;
> > > > + goto err_out;
> >
> > And here too.
> >
> > > > + }
> > > > +
> > > > + notifier = drm_gpusvm_notifier_find(gpusvm, fault_addr);
> > > > + if (!notifier) {
> > > > + notifier = drm_gpusvm_notifier_alloc(gpusvm,
> > > > fault_addr);
> > > > + if (IS_ERR(notifier)) {
> > > > + err = PTR_ERR(notifier);
> > > > + goto err_mmunlock;
> > > > + }
> > > > + notifier_alloc = true;
> > > > + err = mmu_interval_notifier_insert(¬ifier-
> > > > > notifier,
> > > > + mm, notifier-
> > > > > interval.start,
> > > > + notifier-
> > > > > interval.end -
> > > > + notifier-
> > > > > interval.start,
> > > > +
> > > > &drm_gpusvm_notifier_ops);
> > > > + if (err)
> > > > + goto err_notifier;
> > > > + }
> > > > +
> > > > + mmap_read_lock(mm);
> > > > +
> > > > + vas = vma_lookup(mm, fault_addr);
> > > > + if (!vas) {
> > > > + err = -ENOENT;
> > > > + goto err_notifier_remove;
> > > > + }
> > > > +
> > > > + if (!ctx->read_only && !(vas->vm_flags & VM_WRITE)) {
> > > > + err = -EPERM;
> > > > + goto err_notifier_remove;
> > > > + }
> > > > +
> > > > + range = drm_gpusvm_range_find(notifier, fault_addr,
> > > > fault_addr + 1);
> > > > + if (range)
> > > > + goto out_mmunlock;
> > > > + /*
> > > > + * XXX: Short-circuiting migration based on
> > > > migrate_vma_*
> > > > current
> > > > + * limitations. If/when migrate_vma_* add more support,
> > > > this
> > > > logic will
> > > > + * have to change.
> > > > + */
> > > > + migrate_devmem = ctx->devmem_possible &&
> > > > + vma_is_anonymous(vas) &&
> > > > !is_vm_hugetlb_page(vas);
> > > > +
> > > > + chunk_size = drm_gpusvm_range_chunk_size(gpusvm,
> > > > notifier,
> > > > vas,
> > > > + fault_addr,
> > > > gpuva_start,
> > > > + gpuva_end,
> > > > migrate_devmem &&
> > > > + ctx-
> > > > >check_pages);
> > > > + if (chunk_size == LONG_MAX) {
> > > > + err = -EINVAL;
> > > > + goto err_notifier_remove;
> > > > + }
> > > > +
> > > > + range = drm_gpusvm_range_alloc(gpusvm, notifier,
> > > > fault_addr,
> > > > chunk_size,
> > > > + migrate_devmem);
> > > > + if (IS_ERR(range)) {
> > > > + err = PTR_ERR(range);
> > > > + goto err_notifier_remove;
> > > > + }
> > > > +
> > > > + drm_gpusvm_range_insert(notifier, range);
> > > > + if (notifier_alloc)
> > > > + drm_gpusvm_notifier_insert(gpusvm, notifier);
> > > > +
> > > > +out_mmunlock:
> > > > + mmap_read_unlock(mm);
> > > > + mmput(mm);
> > > > +
> > > > + return range;
> > > > +
> > > > +err_notifier_remove:
> > > > + mmap_read_unlock(mm);
> > > > + if (notifier_alloc)
> > > > + mmu_interval_notifier_remove(¬ifier-
> > > > >notifier);
> > > > +err_notifier:
> > > > + if (notifier_alloc)
> > > > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > > > +err_mmunlock:
> > > > + mmput(mm);
> > > > +err_out:
> > > > + return ERR_PTR(err);
> > > > +}
> > > > +
> > > > +/**
> > > > + * __drm_gpusvm_range_unmap_pages - Unmap pages associated with
> > > > a
> > > > GPU SVM range (internal)
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + * @npages: Number of pages to unmap
> > > > + *
> > > > + * This function unmap pages associated with a GPU SVM range.
> > > > Assumes and
> > > > + * asserts correct locking is in place when called.
> > > > + */
> > > > +static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm
> > > > *gpusvm,
> > > > + struct
> > > > drm_gpusvm_range
> > > > *range,
> > > > + unsigned long npages)
> > > > +{
> > > > + unsigned long i, j;
> > > > + struct drm_pagemap *dpagemap = range->dpagemap;
> > > > + struct device *dev = gpusvm->drm->dev;
> > > > +
> > > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > > +
> > > > + if (range->flags.has_dma_mapping) {
> > > > + for (i = 0, j = 0; i < npages; j++) {
> > > > + struct drm_pagemap_dma_addr *addr =
> > > > &range-
> > > > > dma_addr[j];
> > > > +
> > > > + if (addr->proto ==
> > > > DRM_INTERCONNECT_SYSTEM)
> > > > {
> > > > + dma_unmap_page(dev,
> > > > + addr->addr,
> > > > + PAGE_SIZE <<
> > > > addr-
> > > > > order,
> > > > + addr->dir);
> > > > + } else if (dpagemap && dpagemap->ops-
> > > > > unmap_dma) {
> > > > + dpagemap->ops-
> > > > >unmap_dma(dpagemap,
> > > > + dev,
> > > > + *addr);
> > > > + }
> > > > + i += 1 << addr->order;
> > > > + }
> > > > + range->flags.has_devmem_pages = false;
> > > > + range->flags.has_dma_mapping = false;
> > > > + range->dpagemap = NULL;
> > > > + }
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_free_pages - Free pages associated with a
> > > > GPU
> > > > SVM range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + *
> > > > + * This function free pages associated with a GPU SVM range.
> > >
> > > Frees the dma address array
> > >
> >
> > Yes.
> >
> > >
> > > > + */
> > > > +static void drm_gpusvm_range_free_pages(struct drm_gpusvm
> > > > *gpusvm,
> > > > + struct drm_gpusvm_range
> > > > *range)
> > > > +{
> > > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > > +
> > > > + if (range->dma_addr) {
> > > > + kvfree(range->dma_addr);
> > > > + range->dma_addr = NULL;
> > > > + }
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_remove - Remove GPU SVM range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range to be removed
> > > > + *
> > > > + * This function removes the specified GPU SVM range and also
> > > > removes the parent
> > > > + * GPU SVM notifier if no more ranges remain in the notifier.
> > > > The
> > > > caller must
> > > > + * hold a lock to protect range and notifier removal.
> > > > + */
> > > > +void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_range *range)
> > > > +{
> > > > + unsigned long npages = npages_in_range(range->va.start,
> > > > range->va.end);
> > > > + struct drm_gpusvm_notifier *notifier;
> > > > +
> > > > + notifier = drm_gpusvm_notifier_find(gpusvm, range-
> > > > > va.start);
> > > > + if (WARN_ON_ONCE(!notifier))
> > > > + return;
> > > > +
> > > > + drm_gpusvm_notifier_lock(gpusvm);
> > > > + __drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
> > > > + drm_gpusvm_range_free_pages(gpusvm, range);
> > > > + __drm_gpusvm_range_remove(notifier, range);
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > +
> > > > + drm_gpusvm_range_put(range);
> > > > +
> > > > + if (RB_EMPTY_ROOT(¬ifier->root.rb_root)) {
> > > > + if (!notifier->flags.removed)
> > > > + mmu_interval_notifier_remove(¬ifier-
> > > > > notifier);
> > > > + drm_gpusvm_notifier_remove(gpusvm, notifier);
> > > > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > > > + }
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_get - Get a reference to GPU SVM range
> > > > + * @range: Pointer to the GPU SVM range
> > > > + *
> > > > + * This function increments the reference count of the specified
> > > > GPU
> > > > SVM range.
> > > > + *
> > > > + * Returns:
> > > > + * Pointer to the GPU SVM range.
> > > > + */
> > > > +struct drm_gpusvm_range *
> > > > +drm_gpusvm_range_get(struct drm_gpusvm_range *range)
> > > > +{
> > > > + kref_get(&range->refcount);
> > > > +
> > > > + return range;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_destroy - Destroy GPU SVM range
> > > > + * @refcount: Pointer to the reference counter embedded in the
> > > > GPU
> > > > SVM range
> > > > + *
> > > > + * This function destroys the specified GPU SVM range when its
> > > > reference count
> > > > + * reaches zero. If a custom range-free function is provided, it
> > > > is
> > > > invoked to
> > > > + * free the range; otherwise, the range is deallocated using
> > > > kfree().
> > > > + */
> > > > +static void drm_gpusvm_range_destroy(struct kref *refcount)
> > > > +{
> > > > + struct drm_gpusvm_range *range =
> > > > + container_of(refcount, struct drm_gpusvm_range,
> > > > refcount);
> > > > + struct drm_gpusvm *gpusvm = range->gpusvm;
> > > > +
> > > > + if (gpusvm->ops->range_free)
> > > > + gpusvm->ops->range_free(range);
> > > > + else
> > > > + kfree(range);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_put - Put a reference to GPU SVM range
> > > > + * @range: Pointer to the GPU SVM range
> > > > + *
> > > > + * This function decrements the reference count of the specified
> > > > GPU
> > > > SVM range
> > > > + * and frees it when the count reaches zero.
> > > > + */
> > > > +void drm_gpusvm_range_put(struct drm_gpusvm_range *range)
> > > > +{
> > > > + kref_put(&range->refcount, drm_gpusvm_range_destroy);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_pages_valid - GPU SVM range pages valid
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + *
> > > > + * This function determines if a GPU SVM range pages are valid.
> > > > Expected be
> > > > + * called holding gpusvm->notifier_lock and as the last step
> > > > before
> > > > commiting a
> > > > + * GPU binding.
> > > > + *
> > > > + * Returns:
> > > > + * True if GPU SVM range has valid pages, False otherwise
> > > > + */
> > > > +bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_range
> > > > *range)
> > > > +{
> > > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > > +
> > > > + return range->flags.has_devmem_pages || range-
> > > > > flags.has_dma_mapping;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_pages_valid_unlocked - GPU SVM range pages
> > > > valid
> > > > unlocked
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + *
> > > > + * This function determines if a GPU SVM range pages are valid.
> > > > Expected be
> > > > + * called without holding gpusvm->notifier_lock.
> > > > + *
> > > > + * Returns:
> > > > + * True if GPU SVM range has valid pages, False otherwise
> > > > + */
> > > > +static bool
> > > > +drm_gpusvm_range_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_range
> > > > *range)
> > > > +{
> > > > + bool pages_valid;
> > > > +
> > > > + if (!range->dma_addr)
> > > > + return false;
> > > > +
> > > > + drm_gpusvm_notifier_lock(gpusvm);
> > > > + pages_valid = drm_gpusvm_range_pages_valid(gpusvm,
> > > > range);
> > > > + if (!pages_valid)
> > > > + drm_gpusvm_range_free_pages(gpusvm, range);
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > +
> > > > + return pages_valid;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_get_pages - Get pages for a GPU SVM range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + * @ctx: GPU SVM context
> > > > + *
> > > > + * This function gets pages for a GPU SVM range and ensures they
> > > > are
> > > > mapped for
> > > > + * DMA access.
> > > > + *
> > > > + * Returns:
> > > > + * 0 on success, negative error code on failure.
> > > > + */
> > > > +int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_range *range,
> > > > + const struct drm_gpusvm_ctx *ctx)
> > > > +{
> > > > + struct mmu_interval_notifier *notifier = &range-
> > > > >notifier-
> > > > > notifier;
> > > > + struct hmm_range hmm_range = {
> > > > + .default_flags = HMM_PFN_REQ_FAULT | (ctx-
> > > > >read_only
> > > > ? 0 :
> > > > + HMM_PFN_REQ_WRITE),
> > > > + .notifier = notifier,
> > > > + .start = range->va.start,
> > > > + .end = range->va.end,
> > > > + .dev_private_owner = gpusvm-
> > > > > device_private_page_owner,
> > > > + };
> > > > + struct mm_struct *mm = gpusvm->mm;
> > > > + struct drm_gpusvm_zdd *zdd;
> > > > + unsigned long timeout =
> > > > + jiffies +
> > > > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > > > + unsigned long i, j;
> > > > + unsigned long npages = npages_in_range(range->va.start,
> > > > range->va.end);
> > > > + unsigned long num_dma_mapped;
> > > > + unsigned int order = 0;
> > > > + unsigned long *pfns;
> > > > + struct page **pages;
> > > > + int err = 0;
> > > > + struct dev_pagemap *pagemap;
> > > > + struct drm_pagemap *dpagemap;
> > > > +
> > > > +retry:
> > > > + hmm_range.notifier_seq =
> > > > mmu_interval_read_begin(notifier);
> > > > + if (drm_gpusvm_range_pages_valid_unlocked(gpusvm,
> > > > range))
> > > > + goto set_seqno;
> > > > +
> > > > + pfns = kvmalloc_array(npages, sizeof(*pfns),
> > > > GFP_KERNEL);
> > > > + if (!pfns)
> > > > + return -ENOMEM;
> > > > +
> > > > + if (!mmget_not_zero(mm)) {
> > > > + err = -EFAULT;
> > > > + goto err_out;
> > > > + }
> > > > +
> > > > + hmm_range.hmm_pfns = pfns;
> > > > + while (true) {
> > > > + mmap_read_lock(mm);
> > > > + err = hmm_range_fault(&hmm_range);
> > > > + mmap_read_unlock(mm);
> > > > +
> > > > + if (err == -EBUSY) {
> > > > + if (time_after(jiffies, timeout))
> > > > + break;
> > > > +
> > > > + hmm_range.notifier_seq =
> > > > mmu_interval_read_begin(notifier);
> > > > + continue;
> > > > + }
> > > > + break;
> > > > + }
> > > > + mmput(mm);
> > > > + if (err)
> > > > + goto err_free;
> > > > +
> > > > + pages = (struct page **)pfns;
> > > > +map_pages:
> > > > + /*
> > > > + * Perform all dma mappings under the notifier lock to
> > > > not
> > > > + * access freed pages. A notifier will either block on
> > > > + * the notifier lock or unmap dma.
> > > > + */
> > > > + drm_gpusvm_notifier_lock(gpusvm);
> > > > + if (mmu_interval_read_retry(notifier,
> > > > hmm_range.notifier_seq)) {
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > + goto retry;
> > > > + }
> > > > +
> > > > + if (!range->dma_addr) {
> > > > + /* Unlock and restart mapping to allocate
> > > > memory. */
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > + range->dma_addr = kvmalloc_array(npages,
> > > > sizeof(*range->dma_addr),
> > > > + GFP_KERNEL);
> > > > + if (!range->dma_addr) {
> > > > + err = -ENOMEM;
> > > > + goto err_free;
> > > > + }
> > > > + goto map_pages;
> > > > + }
> > > > +
> > > > + zdd = NULL;
> > > > + num_dma_mapped = 0;
> > > > + for (i = 0, j = 0; i < npages; ++j) {
> > > > + struct page *page = hmm_pfn_to_page(pfns[i]);
> > > > +
> > > > + order = hmm_pfn_to_map_order(pfns[i]);
> > > > + if (is_device_private_page(page) ||
> > > > is_device_coherent_page(page)) {
> > > > + if (zdd != page->zone_device_data && i >
> > > > 0)
> > > > {
> > > > + err = -EOPNOTSUPP;
> > > > + goto err_unmap;
> > > > + }
> > > > + zdd = page->zone_device_data;
> > > > + if (pagemap != page->pgmap) {
> > > > + if (i > 0) {
> > > > + err = -EOPNOTSUPP;
> > > > + goto err_unmap;
> > > > + }
> > > > +
> > > > + pagemap = page->pgmap;
> > > > + dpagemap = zdd-
> > > > >devmem_allocation-
> > > > > dpagemap;
> > > > + if (drm_WARN_ON(gpusvm->drm,
> > > > !dpagemap)) {
> > > > + /*
> > > > + * Raced. This is not
> > > > supposed to happen
> > > > + * since
> > > > hmm_range_fault()
> > > > should've migrated
> > > > + * this page to system.
> > > > + */
> > > > + err = -EAGAIN;
> > > > + goto err_unmap;
> > > > + }
> > > > + }
> > > > + range->dma_addr[j] =
> > > > + dpagemap->ops->map_dma(dpagemap,
> > > > gpusvm->drm->dev,
> > > > + page,
> > > > order,
> > > > +
> > > > DMA_BIDIRECTIONAL);
> > > > + if (dma_mapping_error(gpusvm->drm->dev,
> > > > range->dma_addr[j].addr)) {
> > > > + err = -EFAULT;
> > > > + goto err_unmap;
> > > > + }
> > > > +
> > > > + pages[i] = page;
> > > > + } else {
> > > > + dma_addr_t addr;
> > > > +
> > > > + if (is_zone_device_page(page) || zdd) {
> > > > + err = -EOPNOTSUPP;
> > >
> > > I suppose before merging we want to support mixed ranges since
> > > migration is best effort only, or what are the plans here?
> > >
> >
> > I'd say initial merge no mixed support given that adds complexity and
> > the
> > current code is very stable - i.e., get in a simple and stable
> > baseline and then
> > build complexity on top incrementally. I have a lot perf optimization
> > I'd like
> > to get in but omitting for now to stick to the aforementioned plan.
> >
> > Longtern I think a drm_gpusvm_ctx argument will control if we want
> > mixed
> > mappings within a range.
>
> OK.
>
> >
> > > > + goto err_unmap;
> > > > + }
> > > > +
> > > > + addr = dma_map_page(gpusvm->drm->dev,
> > > > + page, 0,
> > > > + PAGE_SIZE << order,
> > > > + DMA_BIDIRECTIONAL);
> > > > + if (dma_mapping_error(gpusvm->drm->dev,
> > > > addr)) {
> > > > + err = -EFAULT;
> > > > + goto err_unmap;
> > > > + }
> > > > +
> > > > + range->dma_addr[j] =
> > > > drm_pagemap_dma_addr_encode
> > > > + (addr, DRM_INTERCONNECT_SYSTEM,
> > > > order,
> > > > + DMA_BIDIRECTIONAL);
> > > > + }
> > > > + i += 1 << order;
> > > > + num_dma_mapped = i;
> > > > + }
> > > > +
> > > > + range->flags.has_dma_mapping = true;
> > > > + if (zdd) {
> > > > + range->flags.has_devmem_pages = true;
> > > > + range->dpagemap = dpagemap;
> > > > + }
> > > > +
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > + kvfree(pfns);
> > > > +set_seqno:
> > > > + range->notifier_seq = hmm_range.notifier_seq;
> > > > +
> > > > + return 0;
> > > > +
> > > > +err_unmap:
> > > > + __drm_gpusvm_range_unmap_pages(gpusvm, range,
> > > > num_dma_mapped);
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > +err_free:
> > > > + kvfree(pfns);
> > > > +err_out:
> > > > + if (err == -EAGAIN)
> > > > + goto retry;
> > > > + return err;
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_range_unmap_pages - Unmap pages associated with a
> > > > GPU
> > > > SVM range
> > > > + * @gpusvm: Pointer to the GPU SVM structure
> > > > + * @range: Pointer to the GPU SVM range structure
> > > > + * @ctx: GPU SVM context
> > > > + *
> > > > + * This function unmaps pages associated with a GPU SVM range.
> > > > If
> > > > @in_notifier
> > > > + * is set, it is assumed that gpusvm->notifier_lock is held in
> > > > write
> > > > mode; if it
> > > > + * is clear, it acquires gpusvm->notifier_lock in read mode.
> > > > Must be
> > > > called on
> > > > + * each GPU SVM range attached to notifier in gpusvm->ops-
> > > > > invalidate for IOMMU
> > > > + * security model.
> > > > + */
> > > > +void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
> > > > + struct drm_gpusvm_range
> > > > *range,
> > > > + const struct drm_gpusvm_ctx
> > > > *ctx)
> > > > +{
> > > > + unsigned long npages = npages_in_range(range->va.start,
> > > > range->va.end);
> > > > +
> > > > + if (ctx->in_notifier)
> > > > + lockdep_assert_held_write(&gpusvm-
> > > > >notifier_lock);
> > > > + else
> > > > + drm_gpusvm_notifier_lock(gpusvm);
> > > > +
> > > > + __drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
> > > > +
> > > > + if (!ctx->in_notifier)
> > > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > > +}
> > >
> > > NIT: Separate functions for locked / unlocked makes life easier for
> > > static code analyzers.
> > >
> >
> > Willl do.
> >
> > >
> > > Section below I think should belong to drm_pagemap.c
> > >
> >
> > Diagree. See my comments on zdd above. Also
> > drm_gpusvm_migration_put_pages uses
> > migration pfns which definitely should not be in drm_pagemap.c.
>
> Like mentioned above, with upcoming populate_mm() moving to being a
> drm_pagemap op, and none of the low level migration helpers taking
> drm_gpusvm as an argument, I think it makes sense, but if you rather
> want to look at shuffling things around when that is in place,
> that's ok. Agree, though that anything needing struct drm_gpusvm should
> *not* be in drm_pagemap.c
>
'but if you rather want to look at shuffling things around when that is in
place'
This sounds like reasonable plan to me - land this first and work through any
reshuffling together in the drm_pagemap.c follow up.
Matt
> Thanks,
> Thomas
>
>
>
> >
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_migration_put_page - Put a migration page
> > > > + * @page: Pointer to the page to put
> > > > + *
> > > > + * This function unlocks and puts a page.
> > > > + */
> > > > +static void drm_gpusvm_migration_put_page(struct page *page)
> > >
> > > _unlock_put_page()?
> > >
> > > > +{
> > > > + unlock_page(page);
> > > > + put_page(page);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_migration_put_pages - Put migration pages
> > > > + * @npages: Number of pages
> > > > + * @migrate_pfn: Array of migrate page frame numbers
> > > > + *
> > > > + * This function puts an array of pages.
> > > > + */
> > > > +static void drm_gpusvm_migration_put_pages(unsigned long npages,
> > > > + unsigned long
> > > > *migrate_pfn)
> > > > +{
> > > > + unsigned long i;
> > > > +
> > > > + for (i = 0; i < npages; ++i) {
> > > > + if (!migrate_pfn[i])
> > > > + continue;
> > > > +
> > > > + drm_gpusvm_migration_put_page(migrate_pfn_to_pag
> > > > e(mi
> > > > grate_pfn[i]));
> > > > + migrate_pfn[i] = 0;
> > > > + }
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_get_devmem_page - Get a reference to a device
> > > > memory
> > > > page
> > > > + * @page: Pointer to the page
> > > > + * @zdd: Pointer to the GPU SVM zone device data
> > > > + *
> > > > + * This function associates the given page with the specified
> > > > GPU
> > > > SVM zone
> > > > + * device data and initializes it for zone device usage.
> > > > + */
> > > > +static void drm_gpusvm_get_devmem_page(struct page *page,
> > > > + struct drm_gpusvm_zdd *zdd)
> > > > +{
> > > > + page->zone_device_data = drm_gpusvm_zdd_get(zdd);
> > > > + zone_device_page_init(page);
> > > > +}
> > > > +
> > > > +/**
> > > > + * drm_gpusvm_migrate_map_pages() - Map migration pages for GPU
> > > > SVM
> > > > migration
> > > > + * @dev: The device for which the pages are being mapped
> > > > + * @dma_addr: Array to store DMA addresses corresponding to
> > > > mapped
> > > > pages
> > > > + * @migrate_pfn: Array of migrate page frame numbers to map
> > > > + * @npages: Number of pages to map
> > > > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> > > > + *
> > > > + * This function maps pages of memory for migration usage in GPU
> > > > SVM. It
> > > > + * iterates over each page frame number provided in
> > > > @migrate_pfn,
> > > > maps the
> > > > + * corresponding page, and stores the DMA address in the
> > > > provided
> > > > @dma_addr
> > > > + * array.
> > > > + *
> > > > + * Return: 0 on success, -EFAULT if an error occurs during
> > > > mapping.
> > > > + */
> > > > +static int drm_gpusvm_migrate_map_pages(struct device *dev,
> > > > + dma_addr_t *dma_addr,
> > > > + long unsigned int
> > > > *migrate_pfn,
> > > > + unsigned long npages,
> > > > + enum dma_data_direction
> > > > dir)
> > > > +{
> > > > + unsigned long i;
> > > > +
> > > > + for (i = 0; i < npages; ++i) {
> > > > + struct page *page =
> > > > migrate_pfn_to_page(migrate_pfn[i]);
> > > > +
> > > > + if (!page)
> > > > + continue;
> > > > +
> > > > + if (WARN_ON_ONCE(is_zone_device_page(page)))
> > > > + return -EFAULT;
> > > > +
> > > > + dma_addr[i] = dma_map_page(dev, page, 0,
> > > > PAGE_SIZE,
> > > > dir);
> > > > + if (dma_mapping_error(dev, dma_addr[i]))
> > > > + return -EFAULT;
> > > > + }
> > > > +
> > > > + return 0;
> > > > +}
> > >
> > > TBC'd
> > >
> >
> > Thanks for the comments!
> >
> > Matt
> >
> > > /Thomas
> > >
>
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