[PATCH v3 0/2] vhost/vsock: fix device IOTLB feature lifecycle

[Jia Jia <physicalmtea@gmail.com>]

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 detaches and frees the old IOTLB when ACCESS_PLATFORM is
cleared. Each virtqueue drops its IOTLB pointer and metadata cache while
holding its own mutex. The old IOTLB remains alive until all virtqueues
have dropped their references. Queued IOTLB miss messages are then
cleared and blocked readers are woken.

Patch 2 keeps the current IOTLB when ACCESS_PLATFORM remains enabled,
so a runtime logging update does not discard valid translations.

Changes since v2:
- update each virtqueue under its own mutex instead of locking all
  virtqueues at once, as suggested by Michael S. Tsirkin
- keep the old IOTLB alive until all per-virtqueue references are gone
- clarify that the teardown drops queued IOTLB miss messages

Changes since v1:
- discard the existing IOTLB instead of returning -EBUSY
- split IOTLB teardown and preservation into separate patches
- clear queued IOTLB miss messages and wake blocked readers

Jia Jia (2):
  vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared
  vhost/vsock: keep IOTLB across feature updates

 drivers/vhost/vsock.c | 42 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

-- 
2.34.1