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

On Thu, Aug 20, 2026 at 04:03:31PM +0800, Jia Jia wrote:

quoted

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 <redacted>
---
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.

quoted

              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