Quoting Joonas Lahtinen (2019-01-07 08:56:55)
> Make sure the underlying VMA in the process address space is the
> same as it was during vm_mmap to avoid applying WC to wrong VMA.
>
> A more long-term solution would be to have vm_mmap_locked variant
> in linux/mmap.h for when caller wants to hold mmap_sem for an
> extended duration.
>
> Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings
> for objects")
> Reported-by: Adam Zabrocki <[email protected]>
> Suggested-by: Linus Torvalds <[email protected]>
> Signed-off-by: Joonas Lahtinen <[email protected]>
> Cc: <[email protected]> # v4.0+
> Cc: Akash Goel <[email protected]>
> Cc: Chris Wilson <[email protected]>
> Cc: Tvrtko Ursulin <[email protected]>
> Cc: Adam Zabrocki <[email protected]>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 062c8395557c..f1d594a53978 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1680,6 +1680,15 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void
> *data,
> return 0;
> }
>
> +static inline bool
> +match_gem_vma(struct vm_area_struct *vma, struct file *filp,
> + unsigned long addr, unsigned long size)
With the exception of there isn't anything gem specific here,
> +{
> + return vma && vma->vm_file == filp &&
> + vma->vm_start == addr &&
> + (vma->vm_end - vma->vm_start) == size;
and we can break this up into separate ifs with a forgiving compiler,
Reviewed-by: Chris Wilson <[email protected]>
I still couldn't see an easy way of passing pgprot bits into do_mmap to
avoid the race entirely.
-Chris
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