[PATCH v7 2/3] vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared

Posted by Jia Jia 1 month, 1 week ago

Clear the device IOTLB when userspace clears VIRTIO_F_ACCESS_PLATFORM.
Otherwise descriptor translation can continue to use mappings installed
before the feature change.

The common helper invalidates cached vring access and applies the
transition even while a backend is attached. The backend remains attached,
but userspace must configure the vring addresses for the new address mode
after a successful live transition.

Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jia Jia <physicalmtea@gmail.com>
---
 drivers/vhost/vsock.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 9aaab6bb8061..e1e9d002d6ae 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -865,9 +865,11 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 		goto err;
 	}
 
-	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
+	if (features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) {
 		if (vhost_init_device_iotlb(&vsock->dev))
 			goto err;
+	} else {
+		vhost_clear_device_iotlb(&vsock->dev);
 	}
 
 	vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
-- 
2.34.1

Re: [PATCH v7 2/3] vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared

Posted by Stefano Garzarella 1 month, 1 week ago

On Thu, Aug 20, 2026 at 04:03:31PM +0800, Jia Jia wrote:
>Clear the device IOTLB when userspace clears VIRTIO_F_ACCESS_PLATFORM.
>Otherwise descriptor translation can continue to use mappings installed
>before the feature change.
>
>The common helper invalidates cached vring access and applies the
>transition even while a backend is attached. The backend remains attached,
>but userspace must configure the vring addresses for the new address mode
>after a successful live transition.
>
>Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")
>Suggested-by: Michael S. Tsirkin <mst@redhat.com>
>Signed-off-by: Jia Jia <physicalmtea@gmail.com>
>---
> drivers/vhost/vsock.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 9aaab6bb8061..e1e9d002d6ae 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -865,9 +865,11 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
> 		goto err;
> 	}
>
>-	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
>+	if (features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) {

Unrelated change...

I think I've already pointed something like this in previous versions: 
for a patch that fixes a specific issue, these unrelated changes should 
be avoided. Please keep this in mind.

Stefano

> 		if (vhost_init_device_iotlb(&vsock->dev))
> 			goto err;
>+	} else {
>+		vhost_clear_device_iotlb(&vsock->dev);
> 	}
>
> 	vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
>-- 
>2.34.1
>

Re: [PATCH v7 2/3] vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared

Posted by Jia Jia 1 month, 1 week ago

>
> On Thu, Aug 20, 2026 at 04:03:31PM +0800, Jia Jia wrote:
> >Clear the device IOTLB when userspace clears VIRTIO_F_ACCESS_PLATFORM.
> >Otherwise descriptor translation can continue to use mappings installed
> >before the feature change.
> >
> >The common helper invalidates cached vring access and applies the
> >transition even while a backend is attached. The backend remains attached,
> >but userspace must configure the vring addresses for the new address mode
> >after a successful live transition.
> >
> >Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")
> >Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> >Signed-off-by: Jia Jia <physicalmtea@gmail.com>
> >---
> > drivers/vhost/vsock.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> >diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> >index 9aaab6bb8061..e1e9d002d6ae 100644
> >--- a/drivers/vhost/vsock.c
> >+++ b/drivers/vhost/vsock.c
> >@@ -865,9 +865,11 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
> >               goto err;
> >       }
> >
> >-      if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
> >+      if (features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) {
>
> Unrelated change...
>
> I think I've already pointed something like this in previous versions:
> for a patch that fixes a specific issue, these unrelated changes should
> be avoided. Please keep this in mind.
>
> Stefano

You're right, thanks for the reminder. That was my oversight—I should
have cleaned it up more carefully. I'll remember that going forward.

>
> >               if (vhost_init_device_iotlb(&vsock->dev))
> >                       goto err;
> >+      } else {
> >+              vhost_clear_device_iotlb(&vsock->dev);
> >       }
> >
> >       vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
> >--
> >2.34.1
> >
>