[Qemu-devel] [PATCH 1/2] vhost-user: add VHOST_USER_RESET_DEVICE to reset devices

[David Vrabel]

Add a VHOST_USER_RESET_DEVICE message which will reset the vhost user
backend. Disabling all rings, and resetting all internal state, ready
for the backend to be reinitialized.

A backend has to report it supports this features with the
VHOST_USER_PROTOCOL_F_RESET_DEVICE protocol feature bit. If it does
so, the new message is used instead of sending a RESET_OWNER which has
had inconsistent implementations.

Signed-off-by: David Vrabel <david.vra...@nutanix.com>
---
 docs/interop/vhost-user.txt | 16 ++++++++++++++++
 hw/virtio/vhost-user.c      |  8 +++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index cb3a7595aa..c5faa9fff8 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -369,6 +369,7 @@ Protocol features
 #define VHOST_USER_PROTOCOL_F_SLAVE_REQ      5
 #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN   6
 #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
+#define VHOST_USER_PROTOCOL_F_RESET_DEVICE   8
 
 Master message types
 --------------------
@@ -689,6 +690,21 @@ Master message types
      feature has been successfully negotiated.
      It's a required feature for crypto devices.
 
+ * VHOST_USER_RESET_DEVICE
+
+      Id: 28
+      Equivalent ioctl: N/A
+      Master payload: N/A
+      Slave payload: N/A
+
+      Ask the vhost user backend to disable all rings and reset all
+      internal device state to the initial state, ready to be
+      reinitialized. The backend retains ownership of the device
+      throughout the reset operation.
+
+      Only valid if the VHOST_USER_PROTOCOL_F_RESET_DEVICE protocol
+      feature is set by the backend.
+
 Slave message types
 -------------------
 
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 41ff5cff41..67207bfe8a 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -41,6 +41,7 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
     VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
     VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
+    VHOST_USER_PROTOCOL_F_RESET_DEVICE = 8,
 
     VHOST_USER_PROTOCOL_F_MAX
 };
@@ -76,6 +77,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_CONFIG = 25,
     VHOST_USER_CREATE_CRYPTO_SESSION = 26,
     VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
+    VHOST_USER_RESET_DEVICE = 28,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -641,10 +643,14 @@ static int vhost_user_set_owner(struct vhost_dev *dev)
 static int vhost_user_reset_device(struct vhost_dev *dev)
 {
     VhostUserMsg msg = {
-        .hdr.request = VHOST_USER_RESET_OWNER,
         .hdr.flags = VHOST_USER_VERSION,
     };
 
+    msg.hdr.request = virtio_has_feature(dev->protocol_features,
+                                         VHOST_USER_PROTOCOL_F_RESET_DEVICE)
+        ? VHOST_USER_RESET_DEVICE
+        : VHOST_USER_RESET_OWNER;
+
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
         return -1;
     }
-- 
2.11.0