5.15-stable review patch. If anyone has any objections, please let me know.
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From: Ville Syrjälä ville.syrjala@linux.intel.com
commit e339c6d628fe66c9b64bf31040a55770952aec57 upstream.
If we can't find a free fence register to handle a fault in the GMADR range just return VM_FAULT_NOPAGE without populating the PTE so that userspace will retry the access and trigger another fault. Eventually we should find a free fence and the fault will get properly handled.
A further improvement idea might be to reserve a fence (or one per CPU?) for the express purpose of handling faults without having to retry. But that would require some additional work.
Looks like this may have gotten broken originally by commit 39965b376601 ("drm/i915: don't trash the gtt when running out of fences") as that changed the errno to -EDEADLK which wasn't handle by the gtt fault code either. But later in commit 2feeb52859fc ("drm/i915/gt: Fix -EDEADLK handling regression") I changed it again to -ENOBUFS as -EDEADLK was now getting used for the ww mutex dance. So this fix only makes sense after that last commit.
Cc: stable@vger.kernel.org Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9479 Fixes: 2feeb52859fc ("drm/i915/gt: Fix -EDEADLK handling regression") Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20231012132801.16292-1-ville.s... Reviewed-by: Andi Shyti andi.shyti@linux.intel.com (cherry picked from commit 7f403caabe811b88ab0de3811ff3f4782c415761) Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/i915/gem/i915_gem_mman.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c @@ -231,6 +231,7 @@ static vm_fault_t i915_error_to_vmf_faul case 0: case -EAGAIN: case -ENOSPC: /* transient failure to evict? */ + case -ENOBUFS: /* temporarily out of fences? */ case -ERESTARTSYS: case -EINTR: case -EBUSY: