Vsock maintains a single CID number space which can be used to communicate to the host (G2H) or to a child-VM (H2G). The current logic trivially assumes that G2H is only relevant for CID <= 2 because these target the hypervisor. However, in environments like Nitro Enclaves, an instance that hosts vhost_vsock powered VMs may still want to communicate to Enclaves that are reachable at higher CIDs through virtio-vsock-pci.
That means that for CID > 2, we really want an overlay. By default, all CIDs are owned by the hypervisor. But if vhost registers a CID, it takes precedence. Implement that logic. Vhost already knows which CIDs it supports anyway. With this logic, I can run a Nitro Enclave as well as a nested VM with vhost-vsock support in parallel, with the parent instance able to communicate to both simultaneously. Signed-off-by: Alexander Graf <[email protected]> --- drivers/vhost/vsock.c | 11 +++++++++++ include/net/af_vsock.h | 3 +++ net/vmw_vsock/af_vsock.c | 3 +++ 3 files changed, 17 insertions(+) diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c index 054f7a718f50..223da817e305 100644 --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -91,6 +91,16 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid, struct net *net) return NULL; } +static bool vhost_transport_has_cid(u32 cid) +{ + bool found; + + rcu_read_lock(); + found = vhost_vsock_get(cid) != NULL; + rcu_read_unlock(); + return found; +} + static void vhost_transport_do_send_pkt(struct vhost_vsock *vsock, struct vhost_virtqueue *vq) @@ -424,6 +434,7 @@ static struct virtio_transport vhost_transport = { .module = THIS_MODULE, .get_local_cid = vhost_transport_get_local_cid, + .has_cid = vhost_transport_has_cid, .init = virtio_transport_do_socket_init, .destruct = virtio_transport_destruct, diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h index 533d8e75f7bb..4cdcb72f9765 100644 --- a/include/net/af_vsock.h +++ b/include/net/af_vsock.h @@ -179,6 +179,9 @@ struct vsock_transport { /* Addressing. */ u32 (*get_local_cid)(void); + /* Check if this transport serves a specific remote CID. */ + bool (*has_cid)(u32 cid); + /* Read a single skb */ int (*read_skb)(struct vsock_sock *, skb_read_actor_t); diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 2f7d94d682cb..8b34b264b246 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -584,6 +584,9 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk) else if (remote_cid <= VMADDR_CID_HOST || !transport_h2g || (remote_flags & VMADDR_FLAG_TO_HOST)) new_transport = transport_g2h; + else if (transport_h2g->has_cid && + !transport_h2g->has_cid(remote_cid)) + new_transport = transport_g2h; else new_transport = transport_h2g; break; -- 2.47.1 Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597
