Re: [Intel-gfx] [RFC v4 06/14] drm/i915/vm_bind: Handle persistent vmas

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On Mon, Sep 26, 2022 at 07:36:24PM -0700, Zeng, Oak wrote:


Regards,
Oak

-----Original Message-----
From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Niranjana
Vishwanathapura
Sent: September 21, 2022 3:10 AM
To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Zanoni, Paulo R <paulo.r.zanoni@xxxxxxxxx>; Hellstrom, Thomas
<thomas.hellstrom@xxxxxxxxx>; Auld, Matthew <matthew.auld@xxxxxxxxx>; Vetter,
Daniel <daniel.vetter@xxxxxxxxx>; christian.koenig@xxxxxxx
Subject: [Intel-gfx] [RFC v4 06/14] drm/i915/vm_bind: Handle persistent vmas

Treat VM_BIND vmas as persistent across execbuf ioctl calls and handle
them during the request submission in the execbuff path.

Support eviction by maintaining a list of evicted persistent vmas
for rebinding during next submission.

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
---
 .../drm/i915/gem/i915_gem_vm_bind_object.c    |  7 +++
 drivers/gpu/drm/i915/gt/intel_gtt.c           |  2 +
 drivers/gpu/drm/i915/gt/intel_gtt.h           |  4 ++
 drivers/gpu/drm/i915/i915_gem_gtt.c           | 39 ++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h           |  3 ++
 drivers/gpu/drm/i915/i915_vma.c               | 46 +++++++++++++++++++
 drivers/gpu/drm/i915/i915_vma.h               | 45 +++++++++++++-----
 drivers/gpu/drm/i915/i915_vma_types.h         | 17 +++++++
 8 files changed, 151 insertions(+), 12 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 7ca6a41fc981..236f901b8b9c 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
@@ -91,6 +91,12 @@ 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);
@@ -181,6 +187,7 @@ static struct i915_vma *vm_bind_get_vma(struct
i915_address_space *vm,

      vma->start = va->start;
      vma->last = va->start + va->length - 1;
+     i915_vma_set_persistent(vma);

      return vma;
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c
b/drivers/gpu/drm/i915/gt/intel_gtt.c
index da4f9dee0397..6db31197fa87 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
@@ -296,6 +296,8 @@ void i915_address_space_init(struct i915_address_space
*vm, int subclass)
      INIT_LIST_HEAD(&vm->non_priv_vm_bind_list);
      vm->root_obj = i915_gem_object_create_internal(vm->i915, PAGE_SIZE);
      GEM_BUG_ON(IS_ERR(vm->root_obj));
+     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 3f2e87d3bf34..b73d35b4e05d 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
@@ -273,6 +273,10 @@ 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_gem_gtt.c
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 329ff75b80b9..b7d0844de561 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -25,6 +25,45 @@
 #include "i915_trace.h"
 #include "i915_vgpu.h"

+/**
+ * i915_vm_sync() - Wait until address space is not in use
+ * @vm: address space
+ *
+ * Waits until all requests using the address space are complete.
+ *
+ * Returns: 0 if success, -ve err code upon failure
+ */
+int i915_vm_sync(struct i915_address_space *vm)
+{
+     int ret;
+
+     /* Wait for all requests under this vm to finish */
+     ret = dma_resv_wait_timeout(vm->root_obj->base.resv,
+                                 DMA_RESV_USAGE_BOOKKEEP, false,
+                                 MAX_SCHEDULE_TIMEOUT);
+     if (ret < 0)
+             return ret;
+     else if (ret > 0)
+             return 0;
+     else
+             return -ETIMEDOUT;
+}
+
+/**
+ * i915_vm_is_active() - Check if address space is being used
+ * @vm: address space
+ *
+ * Check if any request using the specified address space is
+ * active.
+ *
+ * Returns: true if address space is active, false otherwise.
+ */
+bool i915_vm_is_active(const struct i915_address_space *vm)
+{
+     return !dma_resv_test_signaled(vm->root_obj->base.resv,
+                                    DMA_RESV_USAGE_BOOKKEEP);
+}
+
 int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj,
                             struct sg_table *pages)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h
b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 8c2f57eb5dda..a5bbdc59d9df 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -51,4 +51,7 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,

 #define PIN_OFFSET_MASK              I915_GTT_PAGE_MASK

+int i915_vm_sync(struct i915_address_space *vm);
+bool i915_vm_is_active(const struct i915_address_space *vm);
+
 #endif
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index aa332ad69ec2..ff216e9a2c8d 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -237,6 +237,7 @@ 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:
@@ -387,6 +388,24 @@ int i915_vma_wait_for_bind(struct i915_vma *vma)
      return err;
 }

+/**
+ * i915_vma_sync() - Wait for the vma to be idle
+ * @vma: vma to be tested
+ *
+ * Returns 0 on success and error code on failure
+ */
+int i915_vma_sync(struct i915_vma *vma)
+{
+     int ret;
+
+     /* Wait for the asynchronous bindings and pending GPU reads */
+     ret = i915_active_wait(&vma->active);
+     if (ret || !i915_vma_is_persistent(vma) || i915_vma_is_purged(vma))
+             return ret;
+
+     return i915_vm_sync(vma->vm);

Hi, I try to understand why we call vm_sync here. As I understand it, each vm has many vmas. The vma_sync function wait for a single vma to be idle, for example, wait for all the request/gpu task using this vma to complete. While vm_sync wait for the whole vm to be idle. To me vm_sync essentially wait for all the vmas in this vm to be idle. Isn't it?


Yah. But a persistent vma is active as long as the VM is active (also checkout i915_vma_is_active()). Hence we call i915_vm_sync() here.
I am rearranging the patches a bit and this part will go into a separate patch with more description. Hope that will help.

Regards,
Niranjana

Thanks,
Oak

+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
 static int i915_vma_verify_bind_complete(struct i915_vma *vma)
 {
@@ -1654,6 +1673,13 @@ static void force_unbind(struct i915_vma *vma)
      if (!drm_mm_node_allocated(&vma->node))
              return;

+     /*
+      * Mark persistent vma as purged to avoid it waiting
+      * for VM to be released.
+      */
+     if (i915_vma_is_persistent(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));
@@ -1846,6 +1872,8 @@ int _i915_vma_move_to_active(struct i915_vma *vma,
      int err;

      assert_object_held(obj);
+     if (i915_vma_is_persistent(vma))
+             return -EINVAL;

      GEM_BUG_ON(!vma->pages);

@@ -2015,6 +2043,16 @@ 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;
 }

@@ -2046,6 +2084,14 @@ static struct dma_fence
*__i915_vma_unbind_async(struct i915_vma *vma)
              return ERR_PTR(-EBUSY);
      }

+     if (__i915_sw_fence_await_reservation(&vma->resource->chain,
+                                           vma->obj->base.resv,
+                                           DMA_RESV_USAGE_BOOKKEEP,
+                                           i915_fence_timeout(vma->vm->i915),
+                                           I915_FENCE_GFP) < 0) {
+             return ERR_PTR(-EBUSY);
+     }
+
      fence = __i915_vma_evict(vma, true);

      drm_mm_remove_node(&vma->node); /* pairs with i915_vma_release() */
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 6feef0305fe1..aa536c9ce472 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -47,12 +47,6 @@ i915_vma_instance(struct drm_i915_gem_object *obj,

 void i915_vma_unpin_and_release(struct i915_vma **p_vma, unsigned int flags);
 #define I915_VMA_RELEASE_MAP BIT(0)
-
-static inline bool i915_vma_is_active(const struct i915_vma *vma)
-{
-     return !i915_active_is_idle(&vma->active);
-}
-
 /* do not reserve memory to prevent deadlocks */
 #define __EXEC_OBJECT_NO_RESERVE BIT(31)

@@ -138,6 +132,38 @@ static inline u32 i915_ggtt_pin_bias(struct i915_vma *vma)
      return i915_vm_to_ggtt(vma->vm)->pin_bias;
 }

+static inline bool i915_vma_is_persistent(const struct i915_vma *vma)
+{
+     return test_bit(I915_VMA_PERSISTENT_BIT, __i915_vma_flags(vma));
+}
+
+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 bool i915_vma_is_active(const struct i915_vma *vma)
+{
+     if (i915_vma_is_persistent(vma)) {
+             if (i915_vma_is_purged(vma))
+                     return false;
+
+             return i915_vm_is_active(vma->vm);
+     }
+
+     return !i915_active_is_idle(&vma->active);
+}
+
 static inline struct i915_vma *i915_vma_get(struct i915_vma *vma)
 {
      i915_gem_object_get(vma->obj);
@@ -406,12 +432,7 @@ void i915_vma_make_shrinkable(struct i915_vma *vma);
 void i915_vma_make_purgeable(struct i915_vma *vma);

 int i915_vma_wait_for_bind(struct i915_vma *vma);
-
-static inline int i915_vma_sync(struct i915_vma *vma)
-{
-     /* Wait for the asynchronous bindings and pending GPU reads */
-     return i915_active_wait(&vma->active);
-}
+int i915_vma_sync(struct i915_vma *vma);

 /**
  * i915_vma_get_current_resource - Get the current resource of the vma
diff --git a/drivers/gpu/drm/i915/i915_vma_types.h
b/drivers/gpu/drm/i915/i915_vma_types.h
index 6d727c2d9802..d21bf97febaa 100644
--- a/drivers/gpu/drm/i915/i915_vma_types.h
+++ b/drivers/gpu/drm/i915/i915_vma_types.h
@@ -264,6 +264,21 @@ struct i915_vma {
 #define I915_VMA_SCANOUT_BIT 17
 #define I915_VMA_SCANOUT     ((int)BIT(I915_VMA_SCANOUT_BIT))

+  /**
+   * 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
+
+#define I915_VMA_PERSISTENT  ((int)BIT(I915_VMA_PERSISTENT_BIT))
+#define I915_VMA_PURGED              ((int)BIT(I915_VMA_PURGED_BIT))
+
      struct i915_active active;

 #define I915_VMA_PAGES_BIAS 24
@@ -293,6 +308,8 @@ 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 */

--
2.21.0.rc0.32.g243a4c7e27




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