[PATCH 1/4] drm/ttm: add multihop infrastrucutre (v2)
Daniel Vetter
daniel at ffwll.ch
Tue Nov 10 14:34:42 UTC 2020
On Mon, Nov 09, 2020 at 10:54:29AM +1000, Dave Airlie wrote:
> From: Dave Airlie <airlied at redhat.com>
>
> Currently drivers get called to move a buffer, but if they have to
> move it temporarily through another space (SYSTEM->VRAM via TT)
> then they can end up with a lot of ttm->driver->ttm call stacks,
> if the temprorary space moves requires eviction.
>
> Instead of letting the driver do all the placement/space for the
> temporary, allow it to report back (-EMULTIHOP) and a placement (hop)
> to the move code, which will then do the temporary move, and the
> correct placement move afterwards.
>
> This removes a lot of code from drivers, at the expense of
> adding some midlayering. I've some further ideas on how to turn
> it inside out, but I think this is a good solution to the call
> stack problems.
>
> v2: separate out the driver patches, add WARN for getting
> MULTHOP in paths we shouldn't (Daniel)
>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 3 +-
> drivers/gpu/drm/drm_gem_vram_helper.c | 3 +-
> drivers/gpu/drm/nouveau/nouveau_bo.c | 3 +-
> drivers/gpu/drm/qxl/qxl_ttm.c | 3 +-
> drivers/gpu/drm/radeon/radeon_ttm.c | 3 +-
> drivers/gpu/drm/ttm/ttm_bo.c | 68 +++++++++++++++++++---
> drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c | 3 +-
> include/drm/ttm/ttm_bo_driver.h | 7 ++-
> 8 files changed, 77 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index c01c060e4ac5..ce0d82802333 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -656,7 +656,8 @@ static bool amdgpu_mem_visible(struct amdgpu_device *adev,
> */
> static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem)
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop)
> {
> struct amdgpu_device *adev;
> struct amdgpu_bo *abo;
> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
> index 16d68c04ea5d..2cec7b1482b8 100644
> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
> @@ -964,7 +964,8 @@ static void bo_driver_delete_mem_notify(struct ttm_buffer_object *bo)
> static int bo_driver_move(struct ttm_buffer_object *bo,
> bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem)
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop)
> {
> struct drm_gem_vram_object *gbo;
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index 8133377d865d..fee07b9d19ed 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -1023,7 +1023,8 @@ nouveau_bo_vm_cleanup(struct ttm_buffer_object *bo,
> static int
> nouveau_bo_move(struct ttm_buffer_object *bo, bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_reg)
> + struct ttm_resource *new_reg,
> + struct ttm_place *hop)
> {
> struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
> struct nouveau_bo *nvbo = nouveau_bo(bo);
> diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
> index a80d59634143..128c38c8a837 100644
> --- a/drivers/gpu/drm/qxl/qxl_ttm.c
> +++ b/drivers/gpu/drm/qxl/qxl_ttm.c
> @@ -140,7 +140,8 @@ static void qxl_bo_move_notify(struct ttm_buffer_object *bo,
>
> static int qxl_bo_move(struct ttm_buffer_object *bo, bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem)
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop)
> {
> struct ttm_resource *old_mem = &bo->mem;
> int ret;
> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> index 95038ac3382e..29062dbea299 100644
> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> @@ -303,7 +303,8 @@ static int radeon_move_ram_vram(struct ttm_buffer_object *bo,
>
> static int radeon_bo_move(struct ttm_buffer_object *bo, bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem)
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop)
> {
> struct radeon_device *rdev;
> struct radeon_bo *rbo;
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index e2a124b3affb..9f840f2a7836 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -231,7 +231,8 @@ EXPORT_SYMBOL(ttm_bo_bulk_move_lru_tail);
>
> static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
> struct ttm_resource *mem, bool evict,
> - struct ttm_operation_ctx *ctx)
> + struct ttm_operation_ctx *ctx,
> + struct ttm_place *hop)
> {
> struct ttm_bo_device *bdev = bo->bdev;
> struct ttm_resource_manager *old_man = ttm_manager_type(bdev, bo->mem.mem_type);
> @@ -259,9 +260,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
> }
> }
>
> - ret = bdev->driver->move(bo, evict, ctx, mem);
> - if (ret)
> + ret = bdev->driver->move(bo, evict, ctx, mem, hop);
> + if (ret) {
> + if (ret == -EMULTIHOP)
> + return ret;
> goto out_err;
> + }
>
> ctx->bytes_moved += bo->num_pages << PAGE_SHIFT;
> return 0;
> @@ -566,6 +570,7 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
> struct ttm_bo_device *bdev = bo->bdev;
> struct ttm_resource evict_mem;
> struct ttm_placement placement;
> + struct ttm_place hop = {};
> int ret = 0;
>
> dma_resv_assert_held(bo->base.resv);
> @@ -596,8 +601,9 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
> goto out;
> }
>
> - ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, ctx);
> + ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, ctx, &hop);
> if (unlikely(ret)) {
> + WARN(ret == -EMULTIHOP, "Unexpected multihop in eviction - likely driver bug\n");
> if (ret != -ERESTARTSYS)
> pr_err("Buffer eviction failed\n");
> ttm_resource_free(bo, &evict_mem);
> @@ -936,11 +942,39 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
> }
> EXPORT_SYMBOL(ttm_bo_mem_space);
>
> +static int ttm_bo_bounce_temp_buffer(struct ttm_buffer_object *bo,
> + struct ttm_resource *mem,
> + struct ttm_operation_ctx *ctx,
> + struct ttm_place *hop)
> +{
> + struct ttm_placement hop_placement;
> + int ret;
> + struct ttm_resource hop_mem = *mem;
> +
> + hop_mem.mm_node = NULL;
> + hop_mem.mem_type = TTM_PL_SYSTEM;
> + hop_mem.placement = 0;
> +
> + hop_placement.num_placement = hop_placement.num_busy_placement = 1;
> + hop_placement.placement = hop_placement.busy_placement = hop;
> +
> + /* find space in the bounce domain */
> + ret = ttm_bo_mem_space(bo, &hop_placement, &hop_mem, ctx);
> + if (ret)
> + return ret;
> + /* move to the bounce domain */
> + ret = ttm_bo_handle_move_mem(bo, &hop_mem, false, ctx, NULL);
> + if (ret)
> + return ret;
> + return 0;
> +}
> +
> static int ttm_bo_move_buffer(struct ttm_buffer_object *bo,
> struct ttm_placement *placement,
> struct ttm_operation_ctx *ctx)
> {
> int ret = 0;
> + struct ttm_place hop = {};
> struct ttm_resource mem;
>
> dma_resv_assert_held(bo->base.resv);
> @@ -954,12 +988,25 @@ static int ttm_bo_move_buffer(struct ttm_buffer_object *bo,
>
> /*
> * Determine where to move the buffer.
> + *
> + * If driver determines move is going to need
> + * an extra step then it will return -EMULTIHOP
> + * and the buffer will be moved to the temporary
> + * stop and the driver will be called to make
> + * the second hop.
> */
> +bounce:
> ret = ttm_bo_mem_space(bo, placement, &mem, ctx);
> if (ret)
> - goto out_unlock;
> - ret = ttm_bo_handle_move_mem(bo, &mem, false, ctx);
> -out_unlock:
> + return ret;
> + ret = ttm_bo_handle_move_mem(bo, &mem, false, ctx, &hop);
> + if (ret == -EMULTIHOP) {
> + ret = ttm_bo_bounce_temp_buffer(bo, &mem, ctx, &hop);
> + if (ret)
> + return ret;
> + /* try and move to final place now. */
> + goto bounce;
> + }
> if (ret)
> ttm_resource_free(bo, &mem);
> return ret;
> @@ -1432,15 +1479,18 @@ int ttm_bo_swapout(struct ttm_operation_ctx *ctx)
> if (bo->mem.mem_type != TTM_PL_SYSTEM) {
> struct ttm_operation_ctx ctx = { false, false };
> struct ttm_resource evict_mem;
> + struct ttm_place hop = {};
>
> evict_mem = bo->mem;
> evict_mem.mm_node = NULL;
> evict_mem.placement = 0;
> evict_mem.mem_type = TTM_PL_SYSTEM;
>
> - ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, &ctx);
> - if (unlikely(ret != 0))
> + ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, &ctx, &hop);
> + if (unlikely(ret != 0)) {
> + WARN(ret == -EMULTIHOP, "Unexpected multihop in swaput - likely driver bug.\n");
> goto out;
> + }
> }
>
> /**
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
> index 51f70bea41cc..6a04261ce760 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
> @@ -695,7 +695,8 @@ static void vmw_swap_notify(struct ttm_buffer_object *bo)
> static int vmw_move(struct ttm_buffer_object *bo,
> bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem)
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop)
> {
> struct ttm_resource_manager *old_man = ttm_manager_type(bo->bdev, bo->mem.mem_type);
> struct ttm_resource_manager *new_man = ttm_manager_type(bo->bdev, new_mem->mem_type);
> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
> index da8208f43378..f02f7cf9ae90 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -121,6 +121,8 @@ struct ttm_bo_driver {
> * Return the bo flags for a buffer which is not mapped to the hardware.
> * These will be placed in proposed_flags so that when the move is
> * finished, they'll end up in bo->mem.flags
> + * This should not cause multihop evictions, and the core will warn
> + * if one is proposed.
> */
>
> void (*evict_flags)(struct ttm_buffer_object *bo,
> @@ -134,12 +136,15 @@ struct ttm_bo_driver {
> * the graphics address space
> * @ctx: context for this move with parameters
> * @new_mem: the new memory region receiving the buffer
> + @ @hop: placement for driver directed intermediate hop
> *
> * Move a buffer between two memory regions.
> + * Returns errno -EMULTIHOP if driver requests a hop
> */
> int (*move)(struct ttm_buffer_object *bo, bool evict,
> struct ttm_operation_ctx *ctx,
> - struct ttm_resource *new_mem);
> + struct ttm_resource *new_mem,
> + struct ttm_place *hop);
I think the warnings look all good, and everything else too.
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
On the = {} bikeshed I frankly don't care, since for anything where this
matters vs memset you really should have a pad-less structure (by padding
the structure properly). So imo = {} is perfectly fine.
-Daniel
>
> /**
> * struct ttm_bo_driver_member verify_access
> --
> 2.27.0
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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