On Thu, Apr 14, 2022 at 11:19:23AM -0700, Michael Cheng wrote:
Previous concern with using drm_clflush_sg was that we don't know what the sg_table is pointing to, thus the usage of wbinvd_on_all_cpus to flush everything at once to avoid paranoia.
humn... and now we know it is backed by struct pages? I'm not sure I follow what we didn't know before and now we do. Thomas / Matthew, could you take another look herer if it seems correct to you. thanks Lucas De Marchi
To make i915 more architecture-neutral and be less paranoid, lets attempt to use drm_clflush_sg to flush the pages for when the GPU wants to read from main memory. Signed-off-by: Michael Cheng <michael.cheng@xxxxxxxxx> --- drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c index f5062d0c6333..b0a5baaebc43 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c @@ -8,6 +8,7 @@ #include <linux/highmem.h> #include <linux/dma-resv.h> #include <linux/module.h> +#include <drm/drm_cache.h> #include <asm/smp.h> @@ -250,16 +251,10 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj) * DG1 is special here since it still snoops transactions even with * CACHE_NONE. This is not the case with other HAS_SNOOP platforms. We * might need to revisit this as we add new discrete platforms. - * - * XXX: Consider doing a vmap flush or something, where possible. - * Currently we just do a heavy handed wbinvd_on_all_cpus() here since - * the underlying sg_table might not even point to struct pages, so we - * can't just call drm_clflush_sg or similar, like we do elsewhere in - * the driver. */ if (i915_gem_object_can_bypass_llc(obj) || (!HAS_LLC(i915) && !IS_DG1(i915))) - wbinvd_on_all_cpus(); + drm_clflush_sg(pages); sg_page_sizes = i915_sg_dma_sizes(pages->sgl); __i915_gem_object_set_pages(obj, pages, sg_page_sizes); -- 2.25.1
