From 64b1d89f358df34701d92471b65f99f4eff1b384 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 18 May 2017 11:00:15 +0100 Subject: [PATCH] drm/i915: Do not drop pagetables when empty MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Due to a race with the shrinker, when we try to allocate a pagetable, we may end up shrinking it instead. This comes as a nasty surprise as we try to dereference it to fill in the pagetable entries for the object. In linus/master this is fixed by pinning the pagetables prior to allocation, but that backport is roughly drivers/gpu/drm/i915/i915_debugfs.c | 2 +- drivers/gpu/drm/i915/i915_gem_evict.c | 12 +- drivers/gpu/drm/i915/i915_gem_gtt.c | 2017 ++++++++++++++------------------- drivers/gpu/drm/i915/i915_gem_gtt.h | 123 +- drivers/gpu/drm/i915/i915_trace.h | 104 -- drivers/gpu/drm/i915/i915_vgpu.c | 9 +- drivers/gpu/drm/i915/i915_vma.c | 9 - drivers/gpu/drm/i915/intel_lrc.c | 4 +- 8 files changed, 946 insertions(+), 1334 deletions(-) i.e. unsuitable for stable. Instead we neuter the code that tried to free the pagetables. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99295 Fixes: 2ce5179fe826 ("drm/i915/gtt: Free unused lower-level page tables") Signed-off-by: Chris Wilson Cc: Michel Thierry Cc: Mika Kuoppala Cc: Chris Wilson Cc: Joonas Lahtinen Cc: Michał Winiarski Cc: Daniel Vetter Cc: Jani Nikula Cc: intel-gfx@lists.freedesktop.org Cc: # v4.10+ --- drivers/gpu/drm/i915/i915_gem_gtt.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 96e45a4d5441..4f581adf2fcf 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -755,10 +755,6 @@ static bool gen8_ppgtt_clear_pt(struct i915_address_space *vm, GEM_BUG_ON(pte_end > GEN8_PTES); bitmap_clear(pt->used_ptes, pte, num_entries); - if (USES_FULL_PPGTT(vm->i915)) { - if (bitmap_empty(pt->used_ptes, GEN8_PTES)) - return true; - } pt_vaddr = kmap_px(pt); @@ -798,9 +794,6 @@ static bool gen8_ppgtt_clear_pd(struct i915_address_space *vm, } } - if (bitmap_empty(pd->used_pdes, I915_PDES)) - return true; - return false; } @@ -829,9 +822,6 @@ static bool gen8_ppgtt_clear_pdp(struct i915_address_space *vm, mark_tlbs_dirty(ppgtt); - if (bitmap_empty(pdp->used_pdpes, I915_PDPES_PER_PDP(dev_priv))) - return true; - return false; } -- 2.11.0