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[209.85.167.49]) by smtp.gmail.com with ESMTPSA id j19sm235378lfb.90.2019.12.10.17.06.53 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Dec 2019 17:06:54 -0800 (PST) Received: by mail-lf1-f49.google.com with SMTP id 9so15283580lfq.10 for ; Tue, 10 Dec 2019 17:06:53 -0800 (PST) X-Received: by 2002:a05:6512:1dd:: with SMTP id f29mr478455lfp.106.1576026413534; Tue, 10 Dec 2019 17:06:53 -0800 (PST) MIME-Version: 1.0 References: <20191210085759.14763-1-kraxel@redhat.com> In-Reply-To: <20191210085759.14763-1-kraxel@redhat.com> From: Gurchetan Singh Date: Tue, 10 Dec 2019 17:06:42 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] drm/virtio: fix mmap page attributes To: Gerd Hoffmann Cc: ML dri-devel , David Airlie , Daniel Vetter , "open list:VIRTIO GPU DRIVER" , open list Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 10, 2019 at 12:58 AM Gerd Hoffmann wrote: > > virtio-gpu uses cached mappings. shmem helpers use writecombine though. > So roll our own mmap function, wrapping drm_gem_shmem_mmap(), to tweak > vm_page_prot accordingly. > > Reported-by: Gurchetan Singh > Signed-off-by: Gerd Hoffmann > --- > drivers/gpu/drm/virtio/virtgpu_object.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c > index 017a9e0fc3bb..158610902054 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_object.c > +++ b/drivers/gpu/drm/virtio/virtgpu_object.c > @@ -75,6 +75,22 @@ static void virtio_gpu_free_object(struct drm_gem_object *obj) > drm_gem_shmem_free_object(obj); > } > > +static int virtio_gpu_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) > +{ > + pgprot_t prot; > + int ret; > + > + ret = drm_gem_shmem_mmap(obj, vma); > + if (ret < 0) > + return ret; > + > + /* virtio-gpu needs normal caching, so clear writecombine */ > + prot = vm_get_page_prot(vma->vm_flags); > + prot = pgprot_decrypted(prot); > + vma->vm_page_prot = prot; > + return 0; > +} > + > static const struct drm_gem_object_funcs virtio_gpu_gem_funcs = { > .free = virtio_gpu_free_object, > .open = virtio_gpu_gem_object_open, > @@ -86,7 +102,7 @@ static const struct drm_gem_object_funcs virtio_gpu_gem_funcs = { > .get_sg_table = drm_gem_shmem_get_sg_table, > .vmap = drm_gem_shmem_vmap, Do we need vmap/vmunap? It seems optionable and also uses non-cacheable memory? > .vunmap = drm_gem_shmem_vunmap, > - .mmap = &drm_gem_shmem_mmap, > + .mmap = &virtio_gpu_gem_mmap, Why the &virtio_gpu_gem_mmap? Shouldn't just virtio_gpu_gem_mmap work? > }; > > struct drm_gem_object *virtio_gpu_create_object(struct drm_device *dev, > -- > 2.18.1 >