* [PATCH] Revert "virtio: reject shm region if length is zero"
@ 2025-08-07 12:41 Igor Torrente
2025-08-07 12:45 ` Michael S. Tsirkin
0 siblings, 1 reply; 2+ messages in thread
From: Igor Torrente @ 2025-08-07 12:41 UTC (permalink / raw)
To: mst
Cc: sami.md.ko, virtualization, linux-kernel, eperezma, xuanzhuo,
jasowang, dmitry.osipenko, Igor Torrente
This reverts commit 206cc44588f72b49ad4d7e21a7472ab2a72a83df.
Signed-off-by: Igor Torrente <igor.torrente@collabora.com>
---
include/linux/virtio_config.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index b3e1d30c765b..169c7d367fac 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -329,8 +329,6 @@ static inline
bool virtio_get_shm_region(struct virtio_device *vdev,
struct virtio_shm_region *region, u8 id)
{
- if (!region->len)
- return false;
if (!vdev->config->get_shm_region)
return false;
return vdev->config->get_shm_region(vdev, region, id);
--
2.49.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] Revert "virtio: reject shm region if length is zero"
2025-08-07 12:41 [PATCH] Revert "virtio: reject shm region if length is zero" Igor Torrente
@ 2025-08-07 12:45 ` Michael S. Tsirkin
0 siblings, 0 replies; 2+ messages in thread
From: Michael S. Tsirkin @ 2025-08-07 12:45 UTC (permalink / raw)
To: Igor Torrente
Cc: sami.md.ko, virtualization, linux-kernel, eperezma, xuanzhuo,
jasowang, dmitry.osipenko
On Thu, Aug 07, 2025 at 09:41:45AM -0300, Igor Torrente wrote:
> This reverts commit 206cc44588f72b49ad4d7e21a7472ab2a72a83df.
>
No that's not enough. Explain the why not the what.
for example
-------
The commit 206cc44588f7 ("virtio: reject shm region if length is zero")
breaks the Virtio-gpu `host_visible` feature.
As you can see in the snippet below, host_visible_region is zero because
of the `kzalloc`. It's using the `vm_get_shm_region`
(drivers/virtio/virtio_mmio.c:536) to read the `addr` and `len` from
qemu/crosvm.
```
drivers/gpu/drm/virtio/virtgpu_kms.c
132 vgdev = drmm_kzalloc(dev, sizeof(struct virtio_gpu_device), GFP_KERNEL);
[...]
177 if (virtio_get_shm_region(vgdev->vdev, &vgdev->host_visible_region,
178 VIRTIO_GPU_SHM_ID_HOST_VISIBLE)) {
```
Now it always fails.
To fix, revert the offending commit.
Fixes: 206cc44588f7 ("virtio: reject shm region if length is zero` breaks the Virtio-gpu `host_visible")
-------
> Signed-off-by: Igor Torrente <igor.torrente@collabora.com>
> ---
> include/linux/virtio_config.h | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b3e1d30c765b..169c7d367fac 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -329,8 +329,6 @@ static inline
> bool virtio_get_shm_region(struct virtio_device *vdev,
> struct virtio_shm_region *region, u8 id)
> {
> - if (!region->len)
> - return false;
> if (!vdev->config->get_shm_region)
> return false;
> return vdev->config->get_shm_region(vdev, region, id);
> --
> 2.49.0
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2025-08-07 12:46 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-08-07 12:41 [PATCH] Revert "virtio: reject shm region if length is zero" Igor Torrente
2025-08-07 12:45 ` Michael S. Tsirkin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).