[PATCH 3/3] drm/xe/uapi: Introduce VMA bind flag for device atomics
Matthew Brost
matthew.brost at intel.com
Wed Apr 10 17:35:14 UTC 2024
On Wed, Apr 10, 2024 at 07:03:08PM +0200, Nirmoy Das wrote:
> Adds a new VMA bind flag to enable device atomics on SMEM only buffers.
>
> Given that simultaneous usage of device atomics and CPU atomics on
> the same SMEM buffer is not guaranteed to function without migration,
> and UMD expects no migration for SMEM-only buffer objects, so this provide
> a way to set device atomics when UMD is certain to use the buffer only
> for device atomics.
>
For new uAPI we will need a UMD PR using it and provide a link to the PR
in the commit message.
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
> drivers/gpu/drm/xe/xe_vm.c | 27 +++++++++++++++++++++++++--
> drivers/gpu/drm/xe/xe_vm_types.h | 2 ++
> include/uapi/drm/xe_drm.h | 9 +++++----
> 3 files changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 8f3474c5f480..530b4bbc186c 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -851,6 +851,7 @@ static void xe_vma_free(struct xe_vma *vma)
> #define VMA_CREATE_FLAG_READ_ONLY BIT(0)
> #define VMA_CREATE_FLAG_IS_NULL BIT(1)
> #define VMA_CREATE_FLAG_DUMPABLE BIT(2)
> +#define VMA_CREATE_FLAG_DEVICE_ATOMICS BIT(3)
>
> static struct xe_vma *xe_vma_create(struct xe_vm *vm,
> struct xe_bo *bo,
> @@ -864,6 +865,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
> bool read_only = (flags & VMA_CREATE_FLAG_READ_ONLY);
> bool is_null = (flags & VMA_CREATE_FLAG_IS_NULL);
> bool dumpable = (flags & VMA_CREATE_FLAG_DUMPABLE);
> + bool enable_atomics = (flags & VMA_CREATE_FLAG_IS_NULL);
s/flags & VMA_CREATE_FLAG_IS_NULL/flags & VMA_CREATE_FLAG_DEVICE_ATOMICS/
>
> xe_assert(vm->xe, start < end);
> xe_assert(vm->xe, end < vm->size);
> @@ -912,7 +914,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
> xe_bo_assert_held(bo);
>
> if (GRAPHICS_VER(vm->xe) >= 20 || xe_bo_is_vram(bo) ||
> - !IS_DGFX(vm->xe))
> + !IS_DGFX(vm->xe) || enable_atomics)
> vma->gpuva.flags |= XE_VMA_ATOMIC_PTE_BIT;
>
> vm_bo = drm_gpuvm_bo_obtain(vma->gpuva.vm, &bo->ttm.base);
> @@ -2174,6 +2176,18 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_bo *bo,
> operation, (ULL)addr, (ULL)range,
> (ULL)bo_offset_or_userptr);
>
> + if (bo && (flags & DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS) &&
> + (vm->xe->info.platform == XE_PVC && !xe_bo_is_vram(bo))) {
> + drm_warn(&vm->xe->drm, "Setting device atomics on SMEM is not supported for this platform");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + if (bo && (flags & DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS) &&
> + !xe_bo_has_single_placement(bo))
> + drm_warn(&vm->xe->drm, "DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS can be only set if the BO has single placement");
> + return ERR_PTR(-EINVAL);
> + }
> +
A few things here.
- These check should go in xe_vm_bind_ioctl() in the loop that looks up
the BOs and parses them. Probably move implementation to a helper(s)
too as it is already a pretty big ugly loop in xe_vm_bind_ioctl and
adding more logic will make it uglier. Search for
drm_gem_object_lookup in xe_vm_bind_ioctl() for the loop I am refering
to.
- Rather than drm_warns just use XE_IOCTL_DBG for these checks, that is
the style or input to IOCTLs when we return -EINVAL in Xe.
- Are these checks valid? At one point on PVC I had to code to do
atomics between CPU and GPU by migrating the BO back and forth on page
faults. I think the i915 does this too? Are we abandoning that idea?
- Lastly if these check are valid, rather than a platform check in the
code I'd rather see a bit in intel_device_info.
> switch (operation) {
> case DRM_XE_VM_BIND_OP_MAP:
> case DRM_XE_VM_BIND_OP_MAP_USERPTR:
> @@ -2216,6 +2230,7 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_bo *bo,
> if (__op->op == DRM_GPUVA_OP_MAP) {
> op->map.is_null = flags & DRM_XE_VM_BIND_FLAG_NULL;
> op->map.dumpable = flags & DRM_XE_VM_BIND_FLAG_DUMPABLE;
> + op->map.enable_device_atomics = flags & DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS;
> op->map.pat_index = pat_index;
> } else if (__op->op == DRM_GPUVA_OP_PREFETCH) {
> op->prefetch.region = prefetch_region;
> @@ -2412,6 +2427,8 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
> VMA_CREATE_FLAG_IS_NULL : 0;
> flags |= op->map.dumpable ?
> VMA_CREATE_FLAG_DUMPABLE : 0;
> + flags |= op->map.enable_device_atomics ?
> + VMA_CREATE_FLAG_DEVICE_ATOMICS : 0;
>
> vma = new_vma(vm, &op->base.map, op->map.pat_index,
> flags);
> @@ -2439,6 +2456,8 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
> flags |= op->base.remap.unmap->va->flags &
> XE_VMA_DUMPABLE ?
> VMA_CREATE_FLAG_DUMPABLE : 0;
> + flags |= op->base.remap.unmap->va->flags ?
> + VMA_CREATE_FLAG_DEVICE_ATOMICS : 0;
>
> vma = new_vma(vm, op->base.remap.prev,
> old->pat_index, flags);
> @@ -2476,6 +2495,9 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
> flags |= op->base.remap.unmap->va->flags &
> XE_VMA_DUMPABLE ?
> VMA_CREATE_FLAG_DUMPABLE : 0;
> + flags |= op->base.remap.unmap->va->flags ?
> + VMA_CREATE_FLAG_DEVICE_ATOMICS : 0;
> +
Extra newline.
>
> vma = new_vma(vm, op->base.remap.next,
> old->pat_index, flags);
> @@ -2831,7 +2853,8 @@ static int vm_bind_ioctl_ops_execute(struct xe_vm *vm,
> (DRM_XE_VM_BIND_FLAG_READONLY | \
> DRM_XE_VM_BIND_FLAG_IMMEDIATE | \
> DRM_XE_VM_BIND_FLAG_NULL | \
> - DRM_XE_VM_BIND_FLAG_DUMPABLE)
> + DRM_XE_VM_BIND_FLAG_DUMPABLE | \
> + DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS)
> #define XE_64K_PAGE_MASK 0xffffull
> #define ALL_DRM_XE_SYNCS_FLAGS (DRM_XE_SYNCS_FLAG_WAIT_FOR_OP)
>
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
> index badf3945083d..7b9c68909c78 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -282,6 +282,8 @@ struct xe_vma_op_map {
> bool dumpable;
> /** @pat_index: The pat index to use for this operation. */
> u16 pat_index;
> + /** @enable_device_atomics: Whether the VMA will allow device atomics */
> + bool enable_device_atomics;
Put this next to the other bools in xe_vma_op_map.
> };
>
> /** struct xe_vma_op_remap - VMA remap operation */
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 1446c3bae515..bffe8b1c040c 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -969,10 +969,11 @@ struct drm_xe_vm_bind_op {
> /** @op: Bind operation to perform */
> __u32 op;
>
> -#define DRM_XE_VM_BIND_FLAG_READONLY (1 << 0)
> -#define DRM_XE_VM_BIND_FLAG_IMMEDIATE (1 << 1)
> -#define DRM_XE_VM_BIND_FLAG_NULL (1 << 2)
> -#define DRM_XE_VM_BIND_FLAG_DUMPABLE (1 << 3)
> +#define DRM_XE_VM_BIND_FLAG_READONLY (1 << 0)
> +#define DRM_XE_VM_BIND_FLAG_IMMEDIATE (1 << 1)
> +#define DRM_XE_VM_BIND_FLAG_NULL (1 << 2)
> +#define DRM_XE_VM_BIND_FLAG_DUMPABLE (1 << 3)
> +#define DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS (1 << 4)
Kernel doc for new flag.
Matt
> /** @flags: Bind flags */
> __u32 flags;
>
> --
> 2.42.0
>
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