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    Subject[PATCH 4.9 11/25] drm/i915: Fix mismatch between misplaced vma check and vma insert
    Date
    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit 0e53656ad8abc99e0a80c3de611e593ebbf55829 upstream

    When inserting a VMA, we restrict the placement to the low 4G unless the
    caller opts into using the full range. This was done to allow usersapce
    the opportunity to transition slowly from a 32b address space, and to
    avoid breaking inherent 32b assumptions of some commands.

    However, for insert we limited ourselves to 4G-4K, but on verification
    we allowed the full 4G. This causes some attempts to bind a new buffer
    to sporadically fail with -ENOSPC, but at other times be bound
    successfully.

    commit 48ea1e32c39d ("drm/i915/gen9: Set PIN_ZONE_4G end to 4GB - 1
    page") suggests that there is a genuine problem with stateless addressing
    that cannot utilize the last page in 4G and so we purposefully excluded
    it. This means that the quick pin pass may cause us to utilize a buggy
    placement.

    Reported-by: CQ Tang <cq.tang@intel.com>
    Testcase: igt/gem_exec_params/larger-than-life-batch
    Fixes: 48ea1e32c39d ("drm/i915/gen9: Set PIN_ZONE_4G end to 4GB - 1 page")
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: CQ Tang <cq.tang@intel.com>
    Reviewed-by: CQ Tang <cq.tang@intel.com>
    Reviewed-by: Matthew Auld <matthew.auld@intel.com>
    Cc: <stable@vger.kernel.org> # v4.5+
    Link: https://patchwork.freedesktop.org/patch/msgid/20201216092951.7124-1-chris@chris-wilson.co.uk
    (cherry picked from commit 5f22cc0b134ab702d7f64b714e26018f7288ffee)
    Signed-off-by: Jani Nikula <jani.nikula@intel.com>
    [sudip: use file from old path and adjust context]
    Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
    +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
    @@ -882,7 +882,7 @@ eb_vma_misplaced(struct i915_vma *vma)
    return !only_mappable_for_reloc(entry->flags);

    if ((entry->flags & EXEC_OBJECT_SUPPORTS_48B_ADDRESS) == 0 &&
    - (vma->node.start + vma->node.size - 1) >> 32)
    + (vma->node.start + vma->node.size + 4095) >> 32)
    return true;

    return false;

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