[PATCH v4 07/10] Support ram slot configuration in libvhost-user

[Raphael Norwitz <raphael.norwitz@nutanix.com>]

The VHOST_USER_GET_MAX_MEM_SLOTS message allows a vhost-user backend to
specify a maximum number of ram slots it is willing to support. This
change adds support for libvhost-user to process this message. For now
the backend will reply with 8 as the maximum number of regions
supported.

libvhost-user does not yet support the vhost-user protocol feature
VHOST_USER_PROTOCOL_F_CONFIGIRE_MEM_SLOTS, so qemu should never
send the VHOST_USER_GET_MAX_MEM_SLOTS message. Therefore this new
functionality is not currently used.

Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
 contrib/libvhost-user/libvhost-user.c | 19 +++++++++++++++++++
 contrib/libvhost-user/libvhost-user.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index cccfa22..9f039b7 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -137,6 +137,7 @@ vu_request_to_string(unsigned int req)
         REQ(VHOST_USER_SET_INFLIGHT_FD),
         REQ(VHOST_USER_GPU_SET_SOCKET),
         REQ(VHOST_USER_VRING_KICK),
+        REQ(VHOST_USER_GET_MAX_MEM_SLOTS),
         REQ(VHOST_USER_MAX),
     };
 #undef REQ
@@ -1565,6 +1566,22 @@ vu_handle_vring_kick(VuDev *dev, VhostUserMsg *vmsg)
     return false;
 }
 
+static bool vu_handle_get_max_memslots(VuDev *dev, VhostUserMsg *vmsg)
+{
+    vmsg->flags = VHOST_USER_REPLY_MASK | VHOST_USER_VERSION;
+    vmsg->size  = sizeof(vmsg->payload.u64);
+    vmsg->payload.u64 = VHOST_MEMORY_MAX_NREGIONS;
+    vmsg->fd_num = 0;
+
+    if (!vu_message_write(dev, dev->sock, vmsg)) {
+        vu_panic(dev, "Failed to send max ram slots: %s\n", strerror(errno));
+    }
+
+    DPRINT("u64: 0x%016"PRIx64"\n", (uint64_t) VHOST_MEMORY_MAX_NREGIONS);
+
+    return false;
+}
+
 static bool
 vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
 {
@@ -1649,6 +1666,8 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
         return vu_set_inflight_fd(dev, vmsg);
     case VHOST_USER_VRING_KICK:
         return vu_handle_vring_kick(dev, vmsg);
+    case VHOST_USER_GET_MAX_MEM_SLOTS:
+        return vu_handle_get_max_memslots(dev, vmsg);
     default:
         vmsg_close_fds(vmsg);
         vu_panic(dev, "Unhandled request: %d", vmsg->request);
diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
index f30394f..88ef40d 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -97,6 +97,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_INFLIGHT_FD = 32,
     VHOST_USER_GPU_SET_SOCKET = 33,
     VHOST_USER_VRING_KICK = 35,
+    VHOST_USER_GET_MAX_MEM_SLOTS = 36,
     VHOST_USER_MAX
 } VhostUserRequest;
 
-- 
1.8.3.1