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drm/i915: Remove extra multi-gt pm-references

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There was an attempt to fix an issue of illegal attempts to free a still
active i915 VMA object when parking a GT believed to be idle, reported by
CI on 2-GT Meteor Lake.  As a solution, an extra wakeref for a Primary GT
was acquired from i915_gem_do_execbuffer() -- see commit f56fe3e917
("drm/i915: Fix a VMA UAF for multi-gt platform").

However, that fix occurred insufficient -- the issue was still reported by
CI.  That wakeref was released on exit from i915_gem_do_execbuffer(), then
potentially before completion of the request and deactivation of its
associated VMAs.  Moreover, CI reports indicated that single-GT platforms
also suffered sporadically from the same race.

Since the issue has now been fixed by a preceding patch "drm/i915/vma: Fix
UAF on destroy against retire race", drop the no longer useful changes
introduced by that insufficient fix.

v3: Also drop the no longer used .wakeref_gt0 field from struct
    i915_execbuffer.
v2: Avoid the word "revert" in commit message (Rodrigo),
  - update commit description reusing relevant chunks dropped from the
    description of the proper fix (Rodrigo).

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240305143747.335367-7-janusz.krzysztofik@linux.intel.com
This commit is contained in:
Janusz Krzysztofik 2024-03-05 15:35:07 +01:00 committed by Andi Shyti
parent f3c71b2ded
commit 1f33dc0c11
1 changed files with 0 additions and 18 deletions
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18
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
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@ -254,7 +254,6 @@ struct i915_execbuffer {
struct intel_context *context; /* logical state for the request */
struct i915_gem_context *gem_context; /** caller's context */
intel_wakeref_t wakeref;
intel_wakeref_t wakeref_gt0;
/** our requests to build */
struct i915_request *requests[MAX_ENGINE_INSTANCE + 1];
@ -2685,7 +2684,6 @@ static int
eb_select_engine(struct i915_execbuffer *eb)
{
struct intel_context *ce, *child;
struct intel_gt *gt;
unsigned int idx;
int err;
@ -2709,17 +2707,10 @@ eb_select_engine(struct i915_execbuffer *eb)
}
}
eb->num_batches = ce->parallel.number_children + 1;
gt = ce->engine->gt;
for_each_child(ce, child)
intel_context_get(child);
eb->wakeref = intel_gt_pm_get(ce->engine->gt);
/*
* Keep GT0 active on MTL so that i915_vma_parked() doesn't
* free VMAs while execbuf ioctl is validating VMAs.
*/
if (gt->info.id)
eb->wakeref_gt0 = intel_gt_pm_get(to_gt(gt->i915));
if (!test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
err = intel_context_alloc_state(ce);
@ -2758,9 +2749,6 @@ eb_select_engine(struct i915_execbuffer *eb)
return err;
err:
if (gt->info.id)
intel_gt_pm_put(to_gt(gt->i915), eb->wakeref_gt0);
intel_gt_pm_put(ce->engine->gt, eb->wakeref);
for_each_child(ce, child)
intel_context_put(child);
@ -2774,12 +2762,6 @@ eb_put_engine(struct i915_execbuffer *eb)
struct intel_context *child;
i915_vm_put(eb->context->vm);
/*
* This works in conjunction with eb_select_engine() to prevent
* i915_vma_parked() from interfering while execbuf validates vmas.
*/
if (eb->gt->info.id)
intel_gt_pm_put(to_gt(eb->gt->i915), eb->wakeref_gt0);
intel_gt_pm_put(eb->context->engine->gt, eb->wakeref);
for_each_child(eb->context, child)
intel_context_put(child);