Quoting Joonas Lahtinen (2019-01-07 10:56:55)
> 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.
These are now merged to drm-tip, and will head to 5.1 and then
to stable kernels.
Thanks for the report and reviews!
Regards, Joonas
> Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings for objects")
> Reported-by: Adam Zabrocki <adamza@xxxxxxxxxxxxx>
> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.0+
> Cc: Akash Goel <akash.goel@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> Cc: Adam Zabrocki <adamza@xxxxxxxxxxxxx>
> ---
> 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)
> +{
> + return vma && vma->vm_file == filp &&
> + vma->vm_start == addr &&
> + (vma->vm_end - vma->vm_start) == size;
> +}
> +
> /**
> * i915_gem_mmap_ioctl - Maps the contents of an object, returning the address
> * it is mapped to.
> @@ -1738,7 +1747,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
> return -EINTR;
> }
> vma = find_vma(mm, addr);
> - if (vma)
> + if (match_gem_vma(vma, obj->base.filp, addr, args->size))
> vma->vm_page_prot =
> pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> else
> --
> 2.17.2
>
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