Attachment 131404 Details for Bug 99295 – Do not drop pagetables.

[patch] Do not drop pagetables.

0001-drm-i915-Do-not-drop-pagetables-when-empty.patch (text/plain), 2.74 KB, created by Chris Wilson on 2017-05-18 10:06:22 UTC

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Creator: Chris Wilson

Created: 2017-05-18 10:06:22 UTC

Size: 2.74 KB

patch

obsolete

>From 64b1d89f358df34701d92471b65f99f4eff1b384 Mon Sep 17 00:00:00 2001
>From: Chris Wilson <chris@chris-wilson.co.uk>
>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 <chris@chris-wilson.co.uk>
>Cc: Michel Thierry <michel.thierry@intel.com>
>Cc: Mika Kuoppala <mika.kuoppala@intel.com>
>Cc: Chris Wilson <chris@chris-wilson.co.uk>
>Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>Cc: MichaÅ Winiarski <michal.winiarski@intel.com>
>Cc: Daniel Vetter <daniel.vetter@intel.com>
>Cc: Jani Nikula <jani.nikula@linux.intel.com>
>Cc: intel-gfx@lists.freedesktop.org
>Cc: <stable@vger.kernel.org> # 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
>

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