[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 */


More information about the Intel-gfx mailing list