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

[Jia Jia]

Apply the common device IOTLB teardown when userspace clears
VIRTIO_F_ACCESS_PLATFORM. This drops stale translations and avoids
rebuilding an existing IOTLB during feature updates that keep
ACCESS_PLATFORM enabled.

The transition invalidates cached vring access even with an attached
backend. The backend remains attached, but userspace must configure the
vring addresses for the new address mode after a successful live
transition.

Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
Link: https://lore.kernel.org/all/20260726141158.1652386-1-physicalmtea@xxxxxxxxx/
Signed-off-by: Jia Jia <physicalmtea@xxxxxxxxx>
---
 drivers/vhost/net.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 38d9c184082d..4d9d7c2216ed 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1696,6 +1696,8 @@ static int vhost_net_set_features(struct vhost_net *n, const u64 *features)
 	if (virtio_features_test_bit(features, VIRTIO_F_ACCESS_PLATFORM)) {
 		if (vhost_init_device_iotlb(&n->dev))
 			goto out_unlock;
+	} else {
+		vhost_clear_device_iotlb(&n->dev);
 	}
 
 	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
-- 
2.34.1