vhost-vsock leaves the device IOTLB attached when userspace clears
VIRTIO_F_ACCESS_PLATFORM. It also replaces an existing IOTLB with an
empty one whenever a later feature update keeps ACCESS_PLATFORM enabled.

Patch 1 adds a common vhost helper that detaches the device IOTLB from
all virtqueues, clears their metadata caches, drops queued IOTLB miss
messages, and frees the old table after all virtqueues have released
their pointers.

Patch 2 uses the helper when vhost-vsock clears ACCESS_PLATFORM. The
acked_features update remains in the vhost-vsock-specific loop.

Patch 3 avoids replacing an existing IOTLB when ACCESS_PLATFORM remains
enabled across a feature update.

Changes since v3:
- move the IOTLB teardown helper from vhost-vsock into common vhost code
- keep acked_features updates in the backend-specific loop
- add the common helper as a separate first patch

Jia Jia (3):
  vhost: add helper to clear device IOTLB
  vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared
  vhost/vsock: keep IOTLB across feature updates

 drivers/vhost/vhost.c | 24 ++++++++++++++++++++++++
 drivers/vhost/vhost.h |  1 +
 drivers/vhost/vsock.c |  7 ++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

-- 
2.34.1

On Fri, Aug 14, 2026 at 03:29:00PM +0800, Jia Jia wrote:
>vhost-vsock leaves the device IOTLB attached when userspace clears
>VIRTIO_F_ACCESS_PLATFORM. It also replaces an existing IOTLB with an
>empty one whenever a later feature update keeps ACCESS_PLATFORM enabled.
>
>Patch 1 adds a common vhost helper that detaches the device IOTLB from
>all virtqueues, clears their metadata caches, drops queued IOTLB miss
>messages, and frees the old table after all virtqueues have released
>their pointers.

In the v3 you mentioned that this could be used also in vhost-net and 
maybe vhost-scsi. Would it be better to include the other patches in 
this series as well, since we're basically fixing the same issues, or 
have they already been merged?

Thanks,
Stefano

>
>Patch 2 uses the helper when vhost-vsock clears ACCESS_PLATFORM. The
>acked_features update remains in the vhost-vsock-specific loop.
>
>Patch 3 avoids replacing an existing IOTLB when ACCESS_PLATFORM remains
>enabled across a feature update.
>
>Changes since v3:
>- move the IOTLB teardown helper from vhost-vsock into common vhost code
>- keep acked_features updates in the backend-specific loop
>- add the common helper as a separate first patch
>
>Jia Jia (3):
>  vhost: add helper to clear device IOTLB
>  vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared
>  vhost/vsock: keep IOTLB across feature updates
>
> drivers/vhost/vhost.c | 24 ++++++++++++++++++++++++
> drivers/vhost/vhost.h |  1 +
> drivers/vhost/vsock.c |  7 ++++++-
> 3 files changed, 31 insertions(+), 1 deletion(-)
>
>-- 
>2.34.1
>

> In the v3 you mentioned that this could be used also in vhost-net and
> maybe vhost-scsi. Would it be better to include the other patches in
> this series as well, since we're basically fixing the same issues, or
> have they already been merged?

I did not explain this clearly before. vhost-scsi itself does not
negotiate VIRTIO_F_ACCESS_PLATFORM; the fix I referred to addressed a
different issue. See:

20260726144314.1652934-1-physicalmtea@gmail.com

The issue addressed by this series also led me to find corresponding
problems in vhost-net and vhost-vsock. It now appears that these are the
relevant backends here, so I will include the vhost-net changes in this
series as well.

Thanks,
Jia