On Mon, Nov 07, 2022 at 05:39:34PM -0800, Zanoni, Paulo R wrote:
On Mon, 2022-11-07 at 00:52 -0800, Niranjana Vishwanathapura wrote:
Asynchronously unbind the vma upon vm_unbind call.
Fall back to synchronous unbind if backend doesn't support
async unbind or if async unbind fails.
No need for vm_unbind out fence support as i915 will internally
handle all sequencing and user need not try to sequence any
operation with the unbind completion.
Can you please provide some more details on how this works from the
user space point of view? I want to be able to know with 100% certainty
if an unbind has already happened, so I can reuse that vma or whatever
else I may decide to do. I see the interface does not provide any sort
of drm_syncobjs for me to wait on the async unbind. So, when does the
unbind really happen? When can I be sure it's past so I can do stuff
with it? Why would you provide an async ioctl and provide no means for
user space to wait on it?
Paulo,
The async vm_unbind here is not transparent to user space. From user space
point of view, it is like synchronous and they can reuse the assigned virtual
address immediately after vm_unbind ioctl returns. The i915 driver will
ensure that the unbind completes before there is a rebind at that virtual
address. So, unless there is error from user programming where GPU tries to
access the buffer even after user doing the vm_unbind, it should be fine.
Regards,
Niranjana
Thanks,
Paulo
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_vma.c | 51 ++++++++++++++++++++++++++++++---
drivers/gpu/drm/i915/i915_vma.h | 1 +
2 files changed, 48 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 08218e3a2f12..03c966fad87b 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -42,6 +42,8 @@
#include "i915_vma.h"
#include "i915_vma_resource.h"
+static struct dma_fence *__i915_vma_unbind_async(struct i915_vma *vma);
+
static inline void assert_vma_held_evict(const struct i915_vma *vma)
{
/*
@@ -1711,7 +1713,7 @@ void i915_vma_reopen(struct i915_vma *vma)
spin_unlock_irq(>->closed_lock);
}
-static void force_unbind(struct i915_vma *vma)
+static void force_unbind(struct i915_vma *vma, bool async)
{
if (!drm_mm_node_allocated(&vma->node))
return;
@@ -1725,7 +1727,21 @@ static void force_unbind(struct i915_vma *vma)
i915_vma_set_purged(vma);
atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
- WARN_ON(__i915_vma_unbind(vma));
+ if (async) {
+ struct dma_fence *fence;
+
+ fence = __i915_vma_unbind_async(vma);
+ if (IS_ERR_OR_NULL(fence)) {
+ async = false;
+ } else {
+ dma_resv_add_fence(vma->obj->base.resv, fence,
+ DMA_RESV_USAGE_READ);
+ dma_fence_put(fence);
+ }
+ }
+
+ if (!async)
+ WARN_ON(__i915_vma_unbind(vma));
GEM_BUG_ON(drm_mm_node_allocated(&vma->node));
}
@@ -1785,7 +1801,7 @@ void i915_vma_destroy_locked(struct i915_vma *vma)
{
lockdep_assert_held(&vma->vm->mutex);
- force_unbind(vma);
+ force_unbind(vma, false);
list_del_init(&vma->vm_link);
release_references(vma, vma->vm->gt, false);
}
@@ -1796,7 +1812,34 @@ void i915_vma_destroy(struct i915_vma *vma)
bool vm_ddestroy;
mutex_lock(&vma->vm->mutex);
- force_unbind(vma);
+ force_unbind(vma, false);
+ list_del_init(&vma->vm_link);
+ vm_ddestroy = vma->vm_ddestroy;
+ vma->vm_ddestroy = false;
+
+ /* vma->vm may be freed when releasing vma->vm->mutex. */
+ gt = vma->vm->gt;
+ mutex_unlock(&vma->vm->mutex);
+ release_references(vma, gt, vm_ddestroy);
+}
+
+void i915_vma_destroy_async(struct i915_vma *vma)
+{
+ bool vm_ddestroy, async = vma->obj->mm.rsgt;
+ struct intel_gt *gt;
+
+ if (dma_resv_reserve_fences(vma->obj->base.resv, 1))
+ async = false;
+
+ mutex_lock(&vma->vm->mutex);
+ /*
+ * Ensure any asynchronous binding is complete while using
+ * async unbind as we will be releasing the vma here.
+ */
+ if (async && i915_active_wait(&vma->active))
+ async = false;
+
+ force_unbind(vma, async);
list_del_init(&vma->vm_link);
vm_ddestroy = vma->vm_ddestroy;
vma->vm_ddestroy = false;
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 737ef310d046..25f15965dab8 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -272,6 +272,7 @@ void i915_vma_reopen(struct i915_vma *vma);
void i915_vma_destroy_locked(struct i915_vma *vma);
void i915_vma_destroy(struct i915_vma *vma);
+void i915_vma_destroy_async(struct i915_vma *vma);
#define assert_vma_held(vma) dma_resv_assert_held((vma)->obj->base.resv)
