From: Mika Kuoppala Date: Mon, 11 May 2020 16:08:03 +0000 (+0300) Subject: drm/i915/gt: Force pte cacheline to main memory X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=84eac0c65940;p=kernel.git drm/i915/gt: Force pte cacheline to main memory We have problems of tgl not seeing a valid pte entry when iommu is enabled. Add heavy handed flushing of entry modification by flushing the cpu, cacheline and then wcb. This forces the pte out to main memory past this point regarless of promises of coherency. This is an evolution of an experimental patch from Chris Wilson of adding wmb for coherent partners, by adding a clflush to force the cache->memory step. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1840 Testcase: igt/gem_exec_fence/parallel Signed-off-by: Mika Kuoppala Cc: Chris Wilson Reviewed-by: Chris Wilson Signed-off-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20200511160803.15407-1-mika.kuoppala@linux.intel.com --- diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c index 94e746af8926b..2dc88e76ebec8 100644 --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c @@ -389,6 +389,16 @@ static int gen8_ppgtt_alloc(struct i915_address_space *vm, return err; } +static __always_inline inline void +write_pte(gen8_pte_t *pte, const gen8_pte_t val) +{ + /* Magic delays? Or can we refine these to flush all in one pass? */ + *pte = val; + wmb(); /* cpu to cache */ + clflush(pte); /* cache to memory */ + wmb(); /* visible to all */ +} + static __always_inline u64 gen8_ppgtt_insert_pte(struct i915_ppgtt *ppgtt, struct i915_page_directory *pdp, @@ -405,7 +415,8 @@ gen8_ppgtt_insert_pte(struct i915_ppgtt *ppgtt, vaddr = kmap_atomic_px(i915_pt_entry(pd, gen8_pd_index(idx, 1))); do { GEM_BUG_ON(iter->sg->length < I915_GTT_PAGE_SIZE); - vaddr[gen8_pd_index(idx, 0)] = pte_encode | iter->dma; + write_pte(&vaddr[gen8_pd_index(idx, 0)], + pte_encode | iter->dma); iter->dma += I915_GTT_PAGE_SIZE; if (iter->dma >= iter->max) { @@ -487,7 +498,7 @@ static void gen8_ppgtt_insert_huge(struct i915_vma *vma, do { GEM_BUG_ON(iter->sg->length < page_size); - vaddr[index++] = encode | iter->dma; + write_pte(&vaddr[index++], encode | iter->dma); start += page_size; iter->dma += page_size;