[Intel-gfx] [PATCH v3 07/17] drm/i915/vm_bind: Add support to handle object evictions
Matthew Auld
matthew.auld at intel.com
Tue Oct 11 15:48:52 UTC 2022
On 11/10/2022 01:55, Niranjana Vishwanathapura wrote:
> On Mon, Oct 10, 2022 at 05:43:47PM -0700, Niranjana Vishwanathapura wrote:
>> On Mon, Oct 10, 2022 at 06:15:02PM +0100, Matthew Auld wrote:
>>> On 10/10/2022 17:11, Niranjana Vishwanathapura wrote:
>>>> On Mon, Oct 10, 2022 at 02:30:49PM +0100, Matthew Auld wrote:
>>>>> On 10/10/2022 07:58, Niranjana Vishwanathapura wrote:
>>>>>> Support eviction by maintaining a list of evicted persistent vmas
>>>>>> for rebinding during next submission. Ensure the list do not
>>>>>> include persistent vmas that are being purged.
>>>>>>
>>>>>> v2: Remove unused I915_VMA_PURGED definition.
>>>>>> v3: Properly handle __i915_vma_unbind_async() case.
>>>>>>
>>>>>> Acked-by: Matthew Auld <matthew.auld at intel.com>
>>>>>> Signed-off-by: Niranjana Vishwanathapura
>>>>>> <niranjana.vishwanathapura at intel.com>
>>>>>> Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
>>>>>> ---
>>>>>> .../drm/i915/gem/i915_gem_vm_bind_object.c | 6 ++++
>>>>>> drivers/gpu/drm/i915/gt/intel_gtt.c | 2 ++
>>>>>> drivers/gpu/drm/i915/gt/intel_gtt.h | 4 +++
>>>>>> drivers/gpu/drm/i915/i915_vma.c | 31
>>>>>> +++++++++++++++++--
>>>>>> drivers/gpu/drm/i915/i915_vma.h | 10 ++++++
>>>>>> drivers/gpu/drm/i915/i915_vma_types.h | 8 +++++
>>>>>> 6 files changed, 59 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>>>>> b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>>>>> index 8e3e6ceb9442..c435d49af2c8 100644
>>>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>>>>> @@ -85,6 +85,12 @@ static void i915_gem_vm_bind_remove(struct
>>>>>> i915_vma *vma, bool release_obj)
>>>>>> {
>>>>>> lockdep_assert_held(&vma->vm->vm_bind_lock);
>>>>>> + spin_lock(&vma->vm->vm_rebind_lock);
>>>>>> + if (!list_empty(&vma->vm_rebind_link))
>>>>>> + list_del_init(&vma->vm_rebind_link);
>>>>>> + i915_vma_set_purged(vma);
>>>>>> + spin_unlock(&vma->vm->vm_rebind_lock);
>>>>>> +
>>>>>> list_del_init(&vma->vm_bind_link);
>>>>>> list_del_init(&vma->non_priv_vm_bind_link);
>>>>>> i915_vm_bind_it_remove(vma, &vma->vm->va);
>>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c
>>>>>> b/drivers/gpu/drm/i915/gt/intel_gtt.c
>>>>>> index 422394f8fb40..2fa37f46750b 100644
>>>>>> --- a/drivers/gpu/drm/i915/gt/intel_gtt.c
>>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
>>>>>> @@ -295,6 +295,8 @@ void i915_address_space_init(struct
>>>>>> i915_address_space *vm, int subclass)
>>>>>> INIT_LIST_HEAD(&vm->vm_bound_list);
>>>>>> mutex_init(&vm->vm_bind_lock);
>>>>>> INIT_LIST_HEAD(&vm->non_priv_vm_bind_list);
>>>>>> + INIT_LIST_HEAD(&vm->vm_rebind_list);
>>>>>> + spin_lock_init(&vm->vm_rebind_lock);
>>>>>> }
>>>>>> void *__px_vaddr(struct drm_i915_gem_object *p)
>>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h
>>>>>> b/drivers/gpu/drm/i915/gt/intel_gtt.h
>>>>>> index 4ae5734f7d6b..443d1918ad4e 100644
>>>>>> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
>>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
>>>>>> @@ -265,6 +265,10 @@ struct i915_address_space {
>>>>>> struct list_head vm_bind_list;
>>>>>> /** @vm_bound_list: List of vm_binding completed */
>>>>>> struct list_head vm_bound_list;
>>>>>> + /* @vm_rebind_list: list of vmas to be rebinded */
>>>>>> + struct list_head vm_rebind_list;
>>>>>> + /* @vm_rebind_lock: protects vm_rebound_list */
>>>>>> + spinlock_t vm_rebind_lock;
>>>>>> /* @va: tree of persistent vmas */
>>>>>> struct rb_root_cached va;
>>>>>> struct list_head non_priv_vm_bind_list;
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_vma.c
>>>>>> b/drivers/gpu/drm/i915/i915_vma.c
>>>>>> index 5d3d67a4bf47..b4be2cbe8382 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_vma.c
>>>>>> +++ b/drivers/gpu/drm/i915/i915_vma.c
>>>>>> @@ -241,6 +241,7 @@ vma_create(struct drm_i915_gem_object *obj,
>>>>>> INIT_LIST_HEAD(&vma->vm_bind_link);
>>>>>> INIT_LIST_HEAD(&vma->non_priv_vm_bind_link);
>>>>>> + INIT_LIST_HEAD(&vma->vm_rebind_link);
>>>>>> return vma;
>>>>>> err_unlock:
>>>>>> @@ -1686,6 +1687,14 @@ static void force_unbind(struct i915_vma *vma)
>>>>>> if (!drm_mm_node_allocated(&vma->node))
>>>>>> return;
>>>>>> + /*
>>>>>> + * Persistent vma should have been purged by now.
>>>>>> + * If not, issue a warning and purge it.
>>>>>> + */
>>>>>> + if (GEM_WARN_ON(i915_vma_is_persistent(vma) &&
>>>>>> + !i915_vma_is_purged(vma)))
>>>>>> + i915_vma_set_purged(vma);
>>>>>> +
>>>>>> atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
>>>>>> WARN_ON(__i915_vma_unbind(vma));
>>>>>> GEM_BUG_ON(drm_mm_node_allocated(&vma->node));
>>>>>> @@ -2047,6 +2056,16 @@ int __i915_vma_unbind(struct i915_vma *vma)
>>>>>> __i915_vma_evict(vma, false);
>>>>>> drm_mm_remove_node(&vma->node); /* pairs with
>>>>>> i915_vma_release() */
>>>>>> +
>>>>>> + if (i915_vma_is_persistent(vma)) {
>>>>>> + spin_lock(&vma->vm->vm_rebind_lock);
>>>>>> + if (list_empty(&vma->vm_rebind_link) &&
>>>>>> + !i915_vma_is_purged(vma))
>>>>>> + list_add_tail(&vma->vm_rebind_link,
>>>>>> + &vma->vm->vm_rebind_list);
>>>>>> + spin_unlock(&vma->vm->vm_rebind_lock);
>>>>>> + }
>>>>>> +
>>>>>> return 0;
>>>>>> }
>>>>>> @@ -2059,8 +2078,7 @@ static struct dma_fence
>>>>>> *__i915_vma_unbind_async(struct i915_vma *vma)
>>>>>> if (!drm_mm_node_allocated(&vma->node))
>>>>>> return NULL;
>>>>>> - if (i915_vma_is_pinned(vma) ||
>>>>>> - &vma->obj->mm.rsgt->table != vma->resource->bi.pages)
>>>>>
>>>>> Hmm that's looks interesting. IIRC we only keep a ref on the rsgt
>>>>> for the object pages, and not the vma->bi.pages, where the vma
>>>>> pages can be destroyed before the async unbind completes, which I
>>>>> guess was the idea behind this check.
>>>>>
>>>>> But in practice it looks the vma->bi.pages are always just some
>>>>> subset or rearrangement of the objects rsgt pages, if not the same
>>>>> table, so the device mapping pointed at by the PTEs should still be
>>>>> valid here (assuming rsgt in not NULL), even if bi.pages gets
>>>>> nuked? I guess this change should rather be a patch by itself, with
>>>>> proper explanation in commit message, since this looks mostly
>>>>> orthogonal?
>>>>>
>>>>
>>>> Yah, I am not sure about the intent of this check. It is expecting the
>>>> vma->resource->bi.pages to just point to the sg table of the object
>>>> (vma->obj->mm.rsgt->table) which is reference counted, instead of
>>>> decoupling it as you mentioned above. Also, the return code -EAGAIN
>>>> is bit confusing to me as I am not sure how trying again will fix it.
>>>>
>>>> This check was preventing eviction of objects with persistent (vm_bind)
>>>> vmas (Hence the update is in this patch).
>>>> Persistent vmas have I915_GTT_VIEW_PARTIAL, so they will get their
>>>> sg table
>>>> by calling intel_partial_pages() which creates a new sg table
>>>> instead of
>>>> pointing to object's sg table (as done in the I915_GTT_VIEW_NORMAL
>>>> case).]
>>>>
>>>> If the vma is removed before async unbind completes, we probably
>>>> should wait for async unbind to complete before releaseing the vma
>>>> pages? Other option is to have vma point to object's sg table even for
>>>> partial gtt_view (instead of creating a new sg table) and handle
>>>> partial binding during the page table update.
>>>
>>> Yeah, it's a new sg_table, but nothing is actually remmapped in there
>>> it seems, so all the device addresses must map to something already
>>> in obj->mm.rsgt->table (which is ref counted), so all the PTEs will
>>> still be valid, even if the vma is nuked before the unbind actually
>>> completes, AFAICT.
>>>
>>
>> Yah, it is just that vma->pages (hence vma_res.bi.pages), ie., the sg
>> table
>> (if decoupled from obj's sg table) gets freed in __vma_put_pages() before
>> async vma resource is asynchronously unbound and released.
>> This technically seems fine as vma_res.bi.pages are only accessed during
>> binding and not during unbind. But seems bad to keep a pointer dangling
>> after releasing the memory.
>>
>
> Perhaps we can set vma_res->bi.pages to NULL in __vma_put_pages() after
> freeing the vma->pages.
Seems reasonable to me.
>
> Regards,
> Niranjana
>
>> Niranjana
>>
>>>>
>>>> I can also keep the above removed check and only don't check it for
>>>> persistent vmas.
>>>>
>>>> Any thoughts?
>>>>
>>>> Niranjana
>>>>
>>>>>> + if (i915_vma_is_pinned(vma))
>>>>>> return ERR_PTR(-EAGAIN);
>>>>>> /*
>>>>>> @@ -2082,6 +2100,15 @@ static struct dma_fence
>>>>>> *__i915_vma_unbind_async(struct i915_vma *vma)
>>>>>> drm_mm_remove_node(&vma->node); /* pairs with
>>>>>> i915_vma_release() */
>>>>>> + if (i915_vma_is_persistent(vma)) {
>>>>>> + spin_lock(&vma->vm->vm_rebind_lock);
>>>>>> + if (list_empty(&vma->vm_rebind_link) &&
>>>>>> + !i915_vma_is_purged(vma))
>>>>>> + list_add_tail(&vma->vm_rebind_link,
>>>>>> + &vma->vm->vm_rebind_list);
>>>>>> + spin_unlock(&vma->vm->vm_rebind_lock);
>>>>>> + }
>>>>>> +
>>>>>> return fence;
>>>>>> }
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_vma.h
>>>>>> b/drivers/gpu/drm/i915/i915_vma.h
>>>>>> index c5378ec2f70a..9a4a7a8dfe5b 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_vma.h
>>>>>> +++ b/drivers/gpu/drm/i915/i915_vma.h
>>>>>> @@ -152,6 +152,16 @@ static inline void
>>>>>> i915_vma_set_persistent(struct i915_vma *vma)
>>>>>> set_bit(I915_VMA_PERSISTENT_BIT, __i915_vma_flags(vma));
>>>>>> }
>>>>>> +static inline bool i915_vma_is_purged(const struct i915_vma *vma)
>>>>>> +{
>>>>>> + return test_bit(I915_VMA_PURGED_BIT, __i915_vma_flags(vma));
>>>>>> +}
>>>>>> +
>>>>>> +static inline void i915_vma_set_purged(struct i915_vma *vma)
>>>>>> +{
>>>>>> + set_bit(I915_VMA_PURGED_BIT, __i915_vma_flags(vma));
>>>>>> +}
>>>>>> +
>>>>>> static inline struct i915_vma *i915_vma_get(struct i915_vma *vma)
>>>>>> {
>>>>>> i915_gem_object_get(vma->obj);
>>>>>> diff --git a/drivers/gpu/drm/i915/i915_vma_types.h
>>>>>> b/drivers/gpu/drm/i915/i915_vma_types.h
>>>>>> index b8176cca58c0..d32c72e8d242 100644
>>>>>> --- a/drivers/gpu/drm/i915/i915_vma_types.h
>>>>>> +++ b/drivers/gpu/drm/i915/i915_vma_types.h
>>>>>> @@ -267,8 +267,14 @@ struct i915_vma {
>>>>>> /**
>>>>>> * I915_VMA_PERSISTENT_BIT:
>>>>>> * The vma is persistent (created with VM_BIND call).
>>>>>> + *
>>>>>> + * I915_VMA_PURGED_BIT:
>>>>>> + * The persistent vma is force unbound either due to VM_UNBIND call
>>>>>> + * from UMD or VM is released. Do not check/wait for VM activeness
>>>>>> + * in i915_vma_is_active() and i915_vma_sync() calls.
>>>>>> */
>>>>>> #define I915_VMA_PERSISTENT_BIT 19
>>>>>> +#define I915_VMA_PURGED_BIT 20
>>>>>> struct i915_active active;
>>>>>> @@ -299,6 +305,8 @@ struct i915_vma {
>>>>>> struct list_head vm_bind_link;
>>>>>> /* @non_priv_vm_bind_link: Link in non-private persistent VMA
>>>>>> list */
>>>>>> struct list_head non_priv_vm_bind_link;
>>>>>> + /* @vm_rebind_link: link to vm_rebind_list and protected by
>>>>>> vm_rebind_lock */
>>>>>> + struct list_head vm_rebind_link; /* Link in vm_rebind_list */
>>>>>> /** Interval tree structures for persistent vma */
More information about the Intel-gfx
mailing list