RE: [PATCH v3 hyperv-next 3/4] Drivers: hv: vmbus: Enforce 'VMBus version >= 5.2' on isolated guests

Restrict the protocol version(s) that will be negotiated with the host
to be 5.2 or greater if the guest is running isolated.  This reduces the
footprint of the code that will be exercised by Confidential VMs and
hence the exposure to bugs and vulnerabilities.

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
---
 drivers/hv/connection.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 11170d9a2e1a5..c83612cddb995 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c

@@ -244,6 +244,13 @@ int vmbus_connect(void)
 			break;
 	}

+	if (hv_is_isolation_supported() && version < VERSION_WIN10_V5_2) {
+		pr_err("Invalid VMBus version %d.%d (expected >= %d.%d) from the host supporting isolation\n",
+		       version >> 16, version & 0xFFFF, VERSION_WIN10_V5_2 >> 16, VERSION_WIN10_V5_2 & 0xFFFF);
+		ret = -EINVAL;
+		goto cleanup;
+	}
+
 	vmbus_proto_version = version;
 	pr_info("Vmbus version:%d.%d\n",
 		version >> 16, version & 0xFFFF);
--

2.25.1