vmm: config: Add poll_queue property to DiskConfig

Recently, vhost_user_block gained the ability of actively polling the
queue, a feature that can be disabled with the poll_queue property.

This change adds this property to DiskConfig, so it can be used
through the "disk" argument.

For the moment, it can only be used when vhost_user=true, but this
will change once virtio-block gets the poll_queue feature too.

Fixes: #787

Signed-off-by: Sergio Lopez <slp@redhat.com>

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -297,6 +297,9 @@ components:
         wce:
           type: boolean
           default: true
+        poll_queue:
+          type: boolean
+          default: true
 
     NetConfig:
       type: object

vmm/src/config.rs

@@ -41,6 +41,8 @@ pub enum Error {
     ParseDisksParams,
     /// Failed parsing disk queue number parameter.
     ParseDiskNumQueuesParam(std::num::ParseIntError),
+    /// Failed parsing disk poll_queue parameter.
+    ParseDiskPollQueueParam(std::str::ParseBoolError),
     /// Failed parsing disk queue size parameter.
     ParseDiskQueueSizeParam(std::num::ParseIntError),
     /// Failed to parse vhost parameters
@@ -365,6 +367,8 @@ pub struct DiskConfig {
     pub vhost_socket: Option<String>,
     #[serde(default = "default_diskconfig_wce")]
     pub wce: bool,
+    #[serde(default = "default_diskconfig_poll_queue")]
+    pub poll_queue: bool,
 }
 
 fn default_diskconfig_num_queues() -> usize {
@@ -379,6 +383,10 @@ fn default_diskconfig_wce() -> bool {
     true
 }
 
+fn default_diskconfig_poll_queue() -> bool {
+    true
+}
+
 impl DiskConfig {
     pub fn parse(disk: &str) -> Result<Self> {
         // Split the parameters based on the comma delimiter
@@ -393,6 +401,7 @@ impl DiskConfig {
         let mut vhost_socket_str: &str = "";
         let mut vhost_user_str: &str = "";
         let mut wce_str: &str = "";
+        let mut poll_queue_str: &str = "";
 
         for param in params_list.iter() {
             if param.starts_with("path=") {
@@ -413,6 +422,8 @@ impl DiskConfig {
                 vhost_socket_str = &param[7..];
             } else if param.starts_with("wce=") {
                 wce_str = &param[4..];
+            } else if param.starts_with("poll_queue=") {
+                poll_queue_str = &param[11..];
             }
         }
 
@@ -421,6 +432,7 @@ impl DiskConfig {
         let mut vhost_user = false;
         let mut vhost_socket = None;
         let mut wce: bool = default_diskconfig_wce();
+        let mut poll_queue: bool = default_diskconfig_poll_queue();
 
         if !num_queues_str.is_empty() {
             num_queues = num_queues_str
@@ -444,6 +456,14 @@ impl DiskConfig {
             }
             wce = wce_str.parse().map_err(Error::ParseDiskWceParam)?;
         }
+        if !poll_queue_str.is_empty() {
+            if !vhost_user {
+                warn!("poll_queue parameter currently only has effect when used vhost_user=true");
+            }
+            poll_queue = poll_queue_str
+                .parse()
+                .map_err(Error::ParseDiskPollQueueParam)?;
+        }
 
         Ok(DiskConfig {
             path: PathBuf::from(path_str),
@@ -455,6 +475,7 @@ impl DiskConfig {
             vhost_socket,
             vhost_user,
             wce,
+            poll_queue,
         })
     }
 }