Messages in this thread | | | Subject | Re: [PATCH] drm/xen-front: Make shmem backed display buffer coherent | From | Noralf Trønnes <> | Date | Tue, 18 Dec 2018 20:20:22 +0100 |
| |
Den 27.11.2018 11.32, skrev Oleksandr Andrushchenko: > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> > > When GEM backing storage is allocated with drm_gem_get_pages > the backing pages may be cached, thus making it possible that > the backend sees only partial content of the buffer which may > lead to screen artifacts. Make sure that the frontend's > memory is coherent and the backend always sees correct display > buffer content. > > Fixes: c575b7eeb89f ("drm/xen-front: Add support for Xen PV display frontend") > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> > --- > drivers/gpu/drm/xen/xen_drm_front_gem.c | 62 +++++++++++++++++++------ > 1 file changed, 48 insertions(+), 14 deletions(-) > > diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c > index 47ff019d3aef..c592735e49d2 100644 > --- a/drivers/gpu/drm/xen/xen_drm_front_gem.c > +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c > @@ -33,8 +33,11 @@ struct xen_gem_object { > /* set for buffers allocated by the backend */ > bool be_alloc; > > - /* this is for imported PRIME buffer */ > - struct sg_table *sgt_imported; > + /* > + * this is for imported PRIME buffer or the one allocated via > + * drm_gem_get_pages. > + */ > + struct sg_table *sgt; > }; > > static inline struct xen_gem_object * > @@ -77,10 +80,21 @@ static struct xen_gem_object *gem_create_obj(struct drm_device *dev, > return xen_obj; > } > > +struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj) > +{ > + struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj); > + > + if (!xen_obj->pages) > + return ERR_PTR(-ENOMEM); > + > + return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages); > +} > + > static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size) > { > struct xen_drm_front_drm_info *drm_info = dev->dev_private; > struct xen_gem_object *xen_obj; > + struct address_space *mapping; > int ret; > > size = round_up(size, PAGE_SIZE); > @@ -113,10 +127,14 @@ static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size) > xen_obj->be_alloc = true; > return xen_obj; > } > + > /* > * need to allocate backing pages now, so we can share those > * with the backend > */
Let's see if I understand what you're doing:
Here you say that the pages should be DMA accessible for devices that can only see 4GB.
> + mapping = xen_obj->base.filp->f_mapping; > + mapping_set_gfp_mask(mapping, GFP_USER | __GFP_DMA32); > + > xen_obj->num_pages = DIV_ROUND_UP(size, PAGE_SIZE); > xen_obj->pages = drm_gem_get_pages(&xen_obj->base); > if (IS_ERR_OR_NULL(xen_obj->pages)) { > @@ -125,8 +143,27 @@ static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size) > goto fail; > } > > + xen_obj->sgt = xen_drm_front_gem_get_sg_table(&xen_obj->base); > + if (IS_ERR_OR_NULL(xen_obj->sgt)){ > + ret = PTR_ERR(xen_obj->sgt); > + xen_obj->sgt = NULL; > + goto fail_put_pages; > + } > + > + if (!dma_map_sg(dev->dev, xen_obj->sgt->sgl, xen_obj->sgt->nents, > + DMA_BIDIRECTIONAL)) {
Are you using the DMA streaming API as a way to flush the caches? Does this mean that GFP_USER isn't making the buffer coherent?
Noralf.
> + ret = -EFAULT; > + goto fail_free_sgt; > + } > + > return xen_obj; > > +fail_free_sgt: > + sg_free_table(xen_obj->sgt); > + xen_obj->sgt = NULL; > +fail_put_pages: > + drm_gem_put_pages(&xen_obj->base, xen_obj->pages, true, false); > + xen_obj->pages = NULL; > fail: > DRM_ERROR("Failed to allocate buffer with size %zu\n", size); > return ERR_PTR(ret); > @@ -149,7 +186,7 @@ void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj) > struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj); > > if (xen_obj->base.import_attach) { > - drm_prime_gem_destroy(&xen_obj->base, xen_obj->sgt_imported); > + drm_prime_gem_destroy(&xen_obj->base, xen_obj->sgt); > gem_free_pages_array(xen_obj); > } else { > if (xen_obj->pages) { > @@ -158,6 +195,13 @@ void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj) > xen_obj->pages); > gem_free_pages_array(xen_obj); > } else { > + if (xen_obj->sgt) { > + dma_unmap_sg(xen_obj->base.dev->dev, > + xen_obj->sgt->sgl, > + xen_obj->sgt->nents, > + DMA_BIDIRECTIONAL); > + sg_free_table(xen_obj->sgt); > + } > drm_gem_put_pages(&xen_obj->base, > xen_obj->pages, true, false); > } > @@ -174,16 +218,6 @@ struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj) > return xen_obj->pages; > } > > -struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj) > -{ > - struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj); > - > - if (!xen_obj->pages) > - return ERR_PTR(-ENOMEM); > - > - return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages); > -} > - > struct drm_gem_object * > xen_drm_front_gem_import_sg_table(struct drm_device *dev, > struct dma_buf_attachment *attach, > @@ -203,7 +237,7 @@ xen_drm_front_gem_import_sg_table(struct drm_device *dev, > if (ret < 0) > return ERR_PTR(ret); > > - xen_obj->sgt_imported = sgt; > + xen_obj->sgt = sgt; > > ret = drm_prime_sg_to_page_addr_arrays(sgt, xen_obj->pages, > NULL, xen_obj->num_pages);
| |