[PATCH v3 07/17] drm/i915/vm_bind: Add support to handle object evictions
Niranjana Vishwanathapura
niranjana.vishwanathapura at intel.com
Tue Oct 11 00:43:47 UTC 2022
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.
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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