[PATCH v4 3/3] vhost/vsock: keep IOTLB across feature updates

[Jia Jia <physicalmtea@gmail.com>]

VHOST_SET_FEATURES is also used to update logging while a device is
running. When ACCESS_PLATFORM stays enabled, allocating a new empty
IOTLB on every call drops valid translations and forces avoidable
misses.

Initialize the device IOTLB only when one does not already exist.

Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")
Signed-off-by: Jia Jia <physicalmtea@gmail.com>
---
 drivers/vhost/vsock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index b69c260eaeff..9142fa1143b2 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -869,6 +869,7 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 	    vsock->dev.iotlb)
 		vhost_clear_device_iotlb(&vsock->dev);
 
-	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
+	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) &&
+	    !vsock->dev.iotlb) {
 		if (vhost_init_device_iotlb(&vsock->dev))
 			goto err;
-- 
2.34.1