um: virtio: Implement VHOST_USER_PROTOCOL_F_REPLY_ACK

Implement the VHOST_USER_PROTOCOL_F_REPLY_ACK extension for both
slave requests (previous patch) where we have to reply and our
own requests where it helps understand if the slave failed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

2 files changed, 84 insertions, 18 deletions

diff --git a/arch/um/drivers/vhost_user.h b/arch/um/drivers/vhost_user.h
index 8aee9919581e..45ff5ea22fea 100644
--- a/arch/um/drivers/vhost_user.h
+++ b/arch/um/drivers/vhost_user.h
@@ -6,9 +6,11 @@
 
 /* Message flags */
 #define VHOST_USER_FLAG_REPLY           BIT(2)
+#define VHOST_USER_FLAG_NEED_REPLY      BIT(3)
 /* Feature bits */
 #define VHOST_USER_F_PROTOCOL_FEATURES  30
 /* Protocol feature bits */
+#define VHOST_USER_PROTOCOL_F_REPLY_ACK         3
 #define VHOST_USER_PROTOCOL_F_SLAVE_REQ         5
 #define VHOST_USER_PROTOCOL_F_CONFIG            9
 /* Vring state index masks */
@@ -20,7 +22,8 @@
 /* Supported transport features */
 #define VHOST_USER_SUPPORTED_F          BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)
 /* Supported protocol features */
-#define VHOST_USER_SUPPORTED_PROTOCOL_F (BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
+#define VHOST_USER_SUPPORTED_PROTOCOL_F (BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+                                         BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
                                          BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG))
 
 enum vhost_user_request {
diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index ea4d9c1784d2..fc8c52cff5aa 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -160,30 +160,64 @@ static int vhost_user_recv_req(struct virtio_uml_device *vu_dev,
         if (rc)
                 return rc;
 
-        if (msg->header.flags != VHOST_USER_VERSION)
+        if ((msg->header.flags & ~VHOST_USER_FLAG_NEED_REPLY) !=
+                        VHOST_USER_VERSION)
                 return -EPROTO;
 
         return 0;
 }
 
 static int vhost_user_send(struct virtio_uml_device *vu_dev,
-                           struct vhost_user_msg *msg,
+                           bool need_response, struct vhost_user_msg *msg,
                            int *fds, size_t num_fds)
 {
         size_t size = sizeof(msg->header) + msg->header.size;
+        bool request_ack;
+        int rc;
 
         msg->header.flags |= VHOST_USER_VERSION;
-        return full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
+
+        /*
+         * The need_response flag indicates that we already need a response,
+         * e.g. to read the features. In these cases, don't request an ACK as
+         * it is meaningless. Also request an ACK only if supported.
+         */
+        request_ack = !need_response;
+        if (!(vu_dev->protocol_features &
+                        BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK)))
+                request_ack = false;
+
+        if (request_ack)
+                msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
+
+        rc = full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
+        if (rc < 0)
+                return rc;
+
+        if (request_ack) {
+                uint64_t status;
+
+                rc = vhost_user_recv_u64(vu_dev, &status);
+                if (rc)
+                        return rc;
+
+                if (status) {
+                        vu_err(vu_dev, "slave reports error: %llu\n", status);
+                        return -EIO;
+                }
+        }
+
+        return 0;
 }
 
 static int vhost_user_send_no_payload(struct virtio_uml_device *vu_dev,
-                                      u32 request)
+                                      bool need_response, u32 request)
 {
         struct vhost_user_msg msg = {
                 .header.request = request,
         };
 
-        return vhost_user_send(vu_dev, &msg, NULL, 0);
+        return vhost_user_send(vu_dev, need_response, &msg, NULL, 0);
 }
 
 static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
@@ -193,7 +227,7 @@ static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
                 .header.request = request,
         };
 
-        return vhost_user_send(vu_dev, &msg, &fd, 1);
+        return vhost_user_send(vu_dev, false, &msg, &fd, 1);
 }
 
 static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
@@ -205,18 +239,19 @@ static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
                 .payload.integer = value,
         };
 
-        return vhost_user_send(vu_dev, &msg, NULL, 0);
+        return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_owner(struct virtio_uml_device *vu_dev)
 {
-        return vhost_user_send_no_payload(vu_dev, VHOST_USER_SET_OWNER);
+        return vhost_user_send_no_payload(vu_dev, false, VHOST_USER_SET_OWNER);
 }
 
 static int vhost_user_get_features(struct virtio_uml_device *vu_dev,
                                    u64 *features)
 {
-        int rc = vhost_user_send_no_payload(vu_dev, VHOST_USER_GET_FEATURES);
+        int rc = vhost_user_send_no_payload(vu_dev, true,
+                                            VHOST_USER_GET_FEATURES);
 
         if (rc)
                 return rc;
@@ -232,7 +267,7 @@ static int vhost_user_set_features(struct virtio_uml_device *vu_dev,
 static int vhost_user_get_protocol_features(struct virtio_uml_device *vu_dev,
                                             u64 *protocol_features)
 {
-        int rc = vhost_user_send_no_payload(vu_dev,
+        int rc = vhost_user_send_no_payload(vu_dev, true,
                         VHOST_USER_GET_PROTOCOL_FEATURES);
 
         if (rc)
@@ -247,9 +282,32 @@ static int vhost_user_set_protocol_features(struct virtio_uml_device *vu_dev,
                                    protocol_features);
 }
 
+static void vhost_user_reply(struct virtio_uml_device *vu_dev,
+                             struct vhost_user_msg *msg, int response)
+{
+        struct vhost_user_msg reply = {
+                .payload.integer = response,
+        };
+        size_t size = sizeof(reply.header) + sizeof(reply.payload.integer);
+        int rc;
+
+        reply.header = msg->header;
+        reply.header.flags &= ~VHOST_USER_FLAG_NEED_REPLY;
+        reply.header.flags |= VHOST_USER_FLAG_REPLY;
+        reply.header.size = sizeof(reply.payload.integer);
+
+        rc = full_sendmsg_fds(vu_dev->req_fd, &reply, size, NULL, 0);
+
+        if (rc)
+                vu_err(vu_dev,
+                       "sending reply to slave request failed: %d (size %zu)\n",
+                       rc, size);
+}
+
 static irqreturn_t vu_req_interrupt(int irq, void *data)
 {
         struct virtio_uml_device *vu_dev = data;
+        int response = 1;
         struct {
                 struct vhost_user_msg msg;
                 u8 extra_payload[512];
@@ -266,6 +324,7 @@ static irqreturn_t vu_req_interrupt(int irq, void *data)
         switch (msg.msg.header.request) {
         case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG:
                 virtio_config_changed(&vu_dev->vdev);
+                response = 0;
                 break;
         case VHOST_USER_SLAVE_IOTLB_MSG:
                 /* not supported - VIRTIO_F_IOMMU_PLATFORM */
@@ -276,6 +335,9 @@ static irqreturn_t vu_req_interrupt(int irq, void *data)
                        msg.msg.header.request);
         }
 
+        if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)
+                vhost_user_reply(vu_dev, &msg.msg, response);
+
         return IRQ_HANDLED;
 }
 
@@ -365,7 +427,7 @@ static void vhost_user_get_config(struct virtio_uml_device *vu_dev,
         msg->payload.config.offset = 0;
         msg->payload.config.size = cfg_size;
 
-        rc = vhost_user_send(vu_dev, msg, NULL, 0);
+        rc = vhost_user_send(vu_dev, true, msg, NULL, 0);
         if (rc) {
                 vu_err(vu_dev, "sending VHOST_USER_GET_CONFIG failed: %d\n",
                        rc);
@@ -416,7 +478,7 @@ static void vhost_user_set_config(struct virtio_uml_device *vu_dev,
         msg->payload.config.size = len;
         memcpy(msg->payload.config.payload, buf, len);
 
-        rc = vhost_user_send(vu_dev, msg, NULL, 0);
+        rc = vhost_user_send(vu_dev, false, msg, NULL, 0);
         if (rc)
                 vu_err(vu_dev, "sending VHOST_USER_SET_CONFIG failed: %d\n",
                        rc);
@@ -506,7 +568,8 @@ static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
                         return rc;
         }
 
-        return vhost_user_send(vu_dev, &msg, fds, msg.payload.mem_regions.num);
+        return vhost_user_send(vu_dev, false, &msg, fds,
+                               msg.payload.mem_regions.num);
 }
 
 static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
@@ -519,7 +582,7 @@ static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
                 .payload.vring_state.num = num,
         };
 
-        return vhost_user_send(vu_dev, &msg, NULL, 0);
+        return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_vring_num(struct virtio_uml_device *vu_dev,
@@ -550,7 +613,7 @@ static int vhost_user_set_vring_addr(struct virtio_uml_device *vu_dev,
                 .payload.vring_addr.log = log,
         };
 
-        return vhost_user_send(vu_dev, &msg, NULL, 0);
+        return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
@@ -566,9 +629,9 @@ static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
                 return -EINVAL;
         if (fd < 0) {
                 msg.payload.integer |= VHOST_USER_VRING_POLL_MASK;
-                return vhost_user_send(vu_dev, &msg, NULL, 0);
+                return vhost_user_send(vu_dev, false, &msg, NULL, 0);
         }
-        return vhost_user_send(vu_dev, &msg, &fd, 1);
+        return vhost_user_send(vu_dev, false, &msg, &fd, 1);
 }
 
 static int vhost_user_set_vring_call(struct virtio_uml_device *vu_dev,