vhost_user: Add support for ADD_MEM_REG

Adding support for a new message ADD_MEM_REG. This command request a new
region to be added and mapped by the vhost-user backend.

It is designed for supporting memory hotplug, avoiding the limitation
from SET_MEM_TABLE (supports only 8 regions).

It is only available if the protocol feature
VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS has been negotiated.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/vhost_user/master.rs b/src/vhost_user/master.rs
index a721355..d27e4fb 100644
--- a/src/vhost_user/master.rs
+++ b/src/vhost_user/master.rs
@@ -53,6 +53,9 @@ pub trait VhostUserMaster: VhostBackend {
 
     /// Query the maximum amount of memory slots supported by the backend.
     fn get_max_mem_slots(&mut self) -> Result<u64>;
+
+    /// Add a new guest memory mapping for vhost to use.
+    fn add_mem_region(&mut self, region: &VhostUserMemoryRegionInfo) -> Result<()>;
 }
 
 fn error_code<T>(err: VhostUserError) -> Result<T> {
@@ -451,6 +454,27 @@ impl VhostUserMaster for Master {
 
         Ok(val.value)
     }
+
+    fn add_mem_region(&mut self, region: &VhostUserMemoryRegionInfo) -> Result<()> {
+        let mut node = self.node();
+        if node.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits() == 0
+        {
+            return error_code(VhostUserError::InvalidOperation);
+        }
+        if region.memory_size == 0 || region.mmap_handle < 0 {
+            return error_code(VhostUserError::InvalidParam);
+        }
+
+        let body = VhostUserSingleMemoryRegion::new(
+            region.guest_phys_addr,
+            region.memory_size,
+            region.userspace_addr,
+            region.mmap_offset,
+        );
+        let fds = [region.mmap_handle];
+        let hdr = node.send_request_with_body(MasterReq::ADD_MEM_REG, &body, Some(&fds))?;
+        node.wait_for_ack(&hdr).map_err(|e| e.into())
+    }
 }
 
 impl AsRawFd for Master {