[Mesa-dev] [Mesa-stable] [PATCH 1/3] anv: Stop racing relocation offsets

Juan A. Suarez Romero jasuarez at igalia.com
Tue Sep 26 10:31:41 UTC 2017


On Mon, 2017-06-26 at 22:39 +0300, Andres Gomez wrote:
> Jason, it doesn't seem like this patch has landed in master. Are you in
> need of review or is it that this has been superseded?
> 


Gently ping to know what is the status for this patch.

Thaks in advance.


	J.A.

> Thanks!
> 
> On Wed, 2017-05-10 at 16:08 -0700, Jason Ekstrand wrote:
> > One of the key invariants of the relocation system is the
> > presumed_offset field.  The assumption is made that the value currently
> > in the address to be relocated agrees with the presumed_offset field.
> > If presumed_offset is equal to the offset of the BO, the kernel will
> > skip the relocation assuming that the value is already correct.
> > 
> > Our initial implementation of relocation handling had a race where we
> > would read bo->offset once when we wrote the relocation entry and again
> > when we filled out actual address.
> > 
> > Found with helgrind
> > 
> > Cc: "17.0 17.1" <mesa-stable at lists.freedesktop.org>
> > ---
> >  src/intel/vulkan/anv_batch_chain.c | 21 +++++++++++++++++----
> >  src/intel/vulkan/anv_private.h     |  2 +-
> >  src/intel/vulkan/genX_blorp_exec.c |  5 ++++-
> >  src/intel/vulkan/genX_cmd_buffer.c |  7 +++++--
> >  4 files changed, 27 insertions(+), 8 deletions(-)
> > 
> > diff --git a/src/intel/vulkan/anv_batch_chain.c b/src/intel/vulkan/anv_batch_chain.c
> > index 9def174..13303b1 100644
> > --- a/src/intel/vulkan/anv_batch_chain.c
> > +++ b/src/intel/vulkan/anv_batch_chain.c
> > @@ -143,7 +143,8 @@ anv_reloc_list_grow(struct anv_reloc_list *list,
> >  VkResult
> >  anv_reloc_list_add(struct anv_reloc_list *list,
> >                     const VkAllocationCallbacks *alloc,
> > -                   uint32_t offset, struct anv_bo *target_bo, uint32_t delta)
> > +                   uint32_t offset, struct anv_bo *target_bo, uint32_t delta,
> > +                   uint64_t *bo_offset_out)
> >  {
> >     struct drm_i915_gem_relocation_entry *entry;
> >     int index;
> > @@ -155,6 +156,14 @@ anv_reloc_list_add(struct anv_reloc_list *list,
> >     if (result != VK_SUCCESS)
> >        return result;
> >  
> > +   /* Read the BO offset once.  This same value will be used in the relocation
> > +    * entry and passed back to the caller for it to use when it writes the
> > +    * actual value.  This guarantees that the two values match even if there
> > +    * is a data race between now and when the caller gets around to writing
> > +    * the address into the BO.
> > +    */
> > +   uint64_t presumed_offset = target_bo->offset;
> > +
> >     /* XXX: Can we use I915_EXEC_HANDLE_LUT? */
> >     index = list->num_relocs++;
> >     list->reloc_bos[index] = target_bo;
> > @@ -162,11 +171,13 @@ anv_reloc_list_add(struct anv_reloc_list *list,
> >     entry->target_handle = target_bo->gem_handle;
> >     entry->delta = delta;
> >     entry->offset = offset;
> > -   entry->presumed_offset = target_bo->offset;
> > +   entry->presumed_offset = presumed_offset;
> >     entry->read_domains = domain;
> >     entry->write_domain = domain;
> >     VG(VALGRIND_CHECK_MEM_IS_DEFINED(entry, sizeof(*entry)));
> >  
> > +   *bo_offset_out = presumed_offset;
> > +
> >     return VK_SUCCESS;
> >  }
> >  
> > @@ -218,14 +229,16 @@ uint64_t
> >  anv_batch_emit_reloc(struct anv_batch *batch,
> >                       void *location, struct anv_bo *bo, uint32_t delta)
> >  {
> > +   uint64_t bo_offset;
> >     VkResult result = anv_reloc_list_add(batch->relocs, batch->alloc,
> > -                                        location - batch->start, bo, delta);
> > +                                        location - batch->start, bo, delta,
> > +                                        &bo_offset);
> >     if (result != VK_SUCCESS) {
> >        anv_batch_set_error(batch, result);
> >        return 0;
> >     }
> >  
> > -   return bo->offset + delta;
> > +   return bo_offset + delta;
> >  }
> >  
> >  void
> > diff --git a/src/intel/vulkan/anv_private.h b/src/intel/vulkan/anv_private.h
> > index 9b0dd67..1686da8 100644
> > --- a/src/intel/vulkan/anv_private.h
> > +++ b/src/intel/vulkan/anv_private.h
> > @@ -825,7 +825,7 @@ void anv_reloc_list_finish(struct anv_reloc_list *list,
> >  VkResult anv_reloc_list_add(struct anv_reloc_list *list,
> >                              const VkAllocationCallbacks *alloc,
> >                              uint32_t offset, struct anv_bo *target_bo,
> > -                            uint32_t delta);
> > +                            uint32_t delta, uint64_t *bo_offset_out);
> >  
> >  struct anv_batch_bo {
> >     /* Link in the anv_cmd_buffer.owned_batch_bos list */
> > diff --git a/src/intel/vulkan/genX_blorp_exec.c b/src/intel/vulkan/genX_blorp_exec.c
> > index 71ed707..513c269 100644
> > --- a/src/intel/vulkan/genX_blorp_exec.c
> > +++ b/src/intel/vulkan/genX_blorp_exec.c
> > @@ -57,9 +57,12 @@ blorp_surface_reloc(struct blorp_batch *batch, uint32_t ss_offset,
> >                      struct blorp_address address, uint32_t delta)
> >  {
> >     struct anv_cmd_buffer *cmd_buffer = batch->driver_batch;
> > +   MAYBE_UNUSED uint64_t bo_offset;
> > +
> >     VkResult result =
> >        anv_reloc_list_add(&cmd_buffer->surface_relocs, &cmd_buffer->pool->alloc,
> > -                         ss_offset, address.buffer, address.offset + delta);
> > +                         ss_offset, address.buffer, address.offset + delta,
> > +                         &bo_offset);
> >     if (result != VK_SUCCESS)
> >        anv_batch_set_error(&cmd_buffer->batch, result);
> >  }
> > diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
> > index ef9b7d0..4276f59 100644
> > --- a/src/intel/vulkan/genX_cmd_buffer.c
> > +++ b/src/intel/vulkan/genX_cmd_buffer.c
> > @@ -170,10 +170,12 @@ add_surface_state_reloc(struct anv_cmd_buffer *cmd_buffer,
> >                          struct anv_bo *bo, uint32_t offset)
> >  {
> >     const struct isl_device *isl_dev = &cmd_buffer->device->isl_dev;
> > +   MAYBE_UNUSED uint64_t bo_offset;
> >  
> >     VkResult result =
> >        anv_reloc_list_add(&cmd_buffer->surface_relocs, &cmd_buffer->pool->alloc,
> > -                         state.offset + isl_dev->ss.addr_offset, bo, offset);
> > +                         state.offset + isl_dev->ss.addr_offset, bo, offset,
> > +                         &bo_offset);
> >     if (result != VK_SUCCESS)
> >        anv_batch_set_error(&cmd_buffer->batch, result);
> >  }
> > @@ -199,11 +201,12 @@ add_image_view_relocs(struct anv_cmd_buffer *cmd_buffer,
> >        uint32_t *aux_addr_dw = state.map + isl_dev->ss.aux_addr_offset;
> >        aux_offset += *aux_addr_dw & 0xfff;
> >  
> > +      MAYBE_UNUSED uint64_t bo_offset;
> >        VkResult result =
> >           anv_reloc_list_add(&cmd_buffer->surface_relocs,
> >                              &cmd_buffer->pool->alloc,
> >                              state.offset + isl_dev->ss.aux_addr_offset,
> > -                            iview->bo, aux_offset);
> > +                            iview->bo, aux_offset, &bo_offset);
> >        if (result != VK_SUCCESS)
> >           anv_batch_set_error(&cmd_buffer->batch, result);
> >     }


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