From: Dave Airlie airlied@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@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);
/** * struct ttm_bo_driver_member verify_access