On Tue, Dec 08, 2015 at 04:51:18PM +0000, Dave Gordon wrote:
> This patch covers a couple more places where a GEM object is (or may be)
> modified by means of CPU writes, and should therefore be marked dirty to
> ensure that the changes are not lost in the evenof of the object is
> evicted under memory pressure.
>
> It may be possible to optimise these paths later, by marking only
> specific pages of the object as dirty (for objects backed by shmfs
> pages); but for now let's ensure correctness by dirtying the whole
> object.
>
> Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 4 +++-
> drivers/gpu/drm/i915/i915_gem_dmabuf.c | 2 ++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 12f68f4..36b9539 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -937,7 +937,6 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
> i915_gem_object_pin_pages(obj);
>
> offset = args->offset;
> - obj->dirty = 1;
>
> for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents,
> offset >> PAGE_SHIFT) {
> @@ -1074,6 +1073,9 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
> goto out;
> }
>
> + /* Object backing store will be out of date hereafter */
> + obj->dirty = 1;
Possibly. I'd rather just have shmem_pwrite be consistent and use
set_page_dirty. It is baked into the code that it doesn't access every
page.
> trace_i915_gem_object_pwrite(obj, args->offset, args->size);
>
> ret = -EFAULT;
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index e9c2bfd..49a74c6 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -208,6 +208,8 @@ static int i915_gem_begin_cpu_access(struct dma_buf *dma_buf, size_t start, size
> return ret;
>
> ret = i915_gem_object_set_to_cpu_domain(obj, write);
> + if (write)
> + obj->dirty = 1;
No. The accessor here should already be using set_page_dirty.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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