[Intel-gfx] [PATCH v3 07/17] drm/i915/vm_bind: Add support to handle object evictions
Niranjana Vishwanathapura
niranjana.vishwanathapura at intel.com
Tue Oct 11 00:55:32 UTC 2022
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.
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 */
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