Hi,
On Wed, 2024-08-28 at 10:36 +0200, Nirmoy Das wrote:
> This optimization relied on having to clear CCS on allocations.
> If there is no need to clear CCS on allocations then this would
> mostly
> help in reducing CPU utilization.
>
> Revert this patch at this moment because of:
> 1 Currently Xe can't do clear on free and using a invalid ttm flag,
> TTM_TT_FLAG_CLEARED_ON_FREE which could poison global ttm pool on
> multi-device setup.
>
> 2 Also for LNL CPU:WB doesn't require clearing CCS as such BO will
> not be allowed to bind with compression PTE. Subsequent patch will
> disable clearing CCS for CPU:WB BOs for LNL.
>
> This reverts commit 23683061805be368c8d1c7e7ff52abc470cac275.
>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@xxxxxxxxx>
> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
You'd need an Signed-off-by:
With that,
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/xe/xe_bo.c | 26 ++------------------------
> drivers/gpu/drm/xe/xe_device_types.h | 2 --
> drivers/gpu/drm/xe/xe_ttm_sys_mgr.c | 12 ------------
> 3 files changed, 2 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 9d6632f92fa9..25d0c939ba31 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -396,14 +396,6 @@ static struct ttm_tt *xe_ttm_tt_create(struct
> ttm_buffer_object *ttm_bo,
> caching = ttm_uncached;
> }
>
> - /*
> - * If the device can support gpu clear system pages then set
> proper ttm
> - * flag. Zeroed pages are only required for
> ttm_bo_type_device so
> - * unwanted data is not leaked to userspace.
> - */
> - if (ttm_bo->type == ttm_bo_type_device && xe-
> >mem.gpu_page_clear_sys)
> - page_flags |= TTM_TT_FLAG_CLEARED_ON_FREE;
> -
> err = ttm_tt_init(&tt->ttm, &bo->ttm, page_flags, caching,
> extra_pages);
> if (err) {
> kfree(tt);
> @@ -425,10 +417,6 @@ static int xe_ttm_tt_populate(struct ttm_device
> *ttm_dev, struct ttm_tt *tt,
> if (tt->page_flags & TTM_TT_FLAG_EXTERNAL)
> return 0;
>
> - /* Clear TTM_TT_FLAG_ZERO_ALLOC when GPU is set to clear
> system pages */
> - if (tt->page_flags & TTM_TT_FLAG_CLEARED_ON_FREE)
> - tt->page_flags &= ~TTM_TT_FLAG_ZERO_ALLOC;
> -
> err = ttm_pool_alloc(&ttm_dev->pool, tt, ctx);
> if (err)
> return err;
> @@ -671,16 +659,8 @@ static int xe_bo_move(struct ttm_buffer_object
> *ttm_bo, bool evict,
> bool needs_clear;
> bool handle_system_ccs = (!IS_DGFX(xe) &&
> xe_bo_needs_ccs_pages(bo) &&
> ttm && ttm_tt_is_populated(ttm)) ?
> true : false;
> - bool clear_system_pages;
> int ret = 0;
>
> - /*
> - * Clear TTM_TT_FLAG_CLEARED_ON_FREE on bo creation path
> when
> - * moving to system as the bo doesn't have dma_mapping.
> - */
> - if (!old_mem && ttm && !ttm_tt_is_populated(ttm))
> - ttm->page_flags &= ~TTM_TT_FLAG_CLEARED_ON_FREE;
> -
> /* Bo creation path, moving to system or TT. */
> if ((!old_mem && ttm) && !handle_system_ccs) {
> if (new_mem->mem_type == XE_PL_TT)
> @@ -703,10 +683,8 @@ static int xe_bo_move(struct ttm_buffer_object
> *ttm_bo, bool evict,
> move_lacks_source = handle_system_ccs ? (!bo->ccs_cleared)
> :
> (!mem_type_is_vram(o
> ld_mem_type) && !tt_has_data);
>
> - clear_system_pages = ttm && (ttm->page_flags &
> TTM_TT_FLAG_CLEARED_ON_FREE);
> needs_clear = (ttm && ttm->page_flags &
> TTM_TT_FLAG_ZERO_ALLOC) ||
> - (!ttm && ttm_bo->type == ttm_bo_type_device) ||
> - clear_system_pages;
> + (!ttm && ttm_bo->type == ttm_bo_type_device);
>
> if (new_mem->mem_type == XE_PL_TT) {
> ret = xe_tt_map_sg(ttm);
> @@ -818,7 +796,7 @@ static int xe_bo_move(struct ttm_buffer_object
> *ttm_bo, bool evict,
> if (move_lacks_source) {
> u32 flags = 0;
>
> - if (mem_type_is_vram(new_mem->mem_type) ||
> clear_system_pages)
> + if (mem_type_is_vram(new_mem->mem_type))
> flags |= XE_MIGRATE_CLEAR_FLAG_FULL;
> else if (handle_system_ccs)
> flags |=
> XE_MIGRATE_CLEAR_FLAG_CCS_DATA;
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h
> b/drivers/gpu/drm/xe/xe_device_types.h
> index 4ecd620921a3..e73fb0c23932 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -333,8 +333,6 @@ struct xe_device {
> struct xe_mem_region vram;
> /** @mem.sys_mgr: system TTM manager */
> struct ttm_resource_manager sys_mgr;
> - /** @mem.gpu_page_clear_sys: clear system pages
> offloaded to GPU */
> - bool gpu_page_clear_sys;
> } mem;
>
> /** @sriov: device level virtualization data */
> diff --git a/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> b/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> index e0ac20f20758..9844a8edbfe1 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> +++ b/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> @@ -117,17 +117,5 @@ int xe_ttm_sys_mgr_init(struct xe_device *xe)
> ttm_resource_manager_init(man, &xe->ttm, gtt_size >>
> PAGE_SHIFT);
> ttm_set_driver_manager(&xe->ttm, XE_PL_TT, man);
> ttm_resource_manager_set_used(man, true);
> -
> - /*
> - * On iGFX device with flat CCS, we clear CCS metadata,
> let's extend that
> - * and use GPU to clear pages as well.
> - *
> - * Disable this when init_on_free and/or init_on_alloc is on
> to avoid double
> - * zeroing pages with CPU and GPU.
> - */
> - if (xe_device_has_flat_ccs(xe) && !IS_DGFX(xe) &&
> - !want_init_on_alloc(GFP_USER) && !want_init_on_free())
> - xe->mem.gpu_page_clear_sys = true;
> -
> return drmm_add_action_or_reset(&xe->drm, ttm_sys_mgr_fini,
> xe);
> }
