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need of review or is it that this has been superseded?
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-sta...@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);
> }
--
Br,
Andres
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