Hi,
On Thu, Feb 07, 2019 at 10:54:53AM +0200, Joonas Lahtinen wrote:
> 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.
>
It seems like we may have a regression due to this patch. I am still
debugging, but I have a question; please see below.
Thanks,
Guenter
> v2:
> - Refactor the compare function
>
> 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>
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> #v1
> ---
> drivers/gpu/drm/i915/i915_gem.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 05ce9176ac4e..52639f749908 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1681,6 +1681,16 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data,
> return 0;
> }
>
> +static inline bool
> +__vma_matches(struct vm_area_struct *vma, struct file *filp,
> + unsigned long addr, unsigned long size)
> +{
> + if (vma->vm_file != filp)
> + return false;
> +
> + return vma->vm_start == addr && (vma->vm_end - vma->vm_start) == size;
Shouldn't this be:
return vma->vm_start == addr && (vma->vm_end - vma->vm_start + 1) == size;
instead ?
> +}
> +
> /**
> * i915_gem_mmap_ioctl - Maps the contents of an object, returning the address
> * it is mapped to.
> @@ -1739,7 +1749,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
> return -EINTR;
> }
> vma = find_vma(mm, addr);
> - if (vma)
> + if (vma && __vma_matches(vma, obj->base.filp, addr, args->size))
> vma->vm_page_prot =
> pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> else
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