virtio-devices: vhost_user: Factorize features negotiation

Factorize the virtio features and vhost-user protocol features
negotiation through a common function that blk, fs and net
implementations can directly rely on.

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

virtio-devices/src/vhost_user/blk.rs

@@ -46,6 +46,9 @@ impl Blk {
     pub fn new(id: String, vu_cfg: VhostUserConfig) -> Result<Blk> {
         let num_queues = vu_cfg.num_queues;
 
+        let mut vhost_user_blk = Master::connect(&vu_cfg.socket, num_queues as u64)
+            .map_err(Error::VhostUserCreateMaster)?;
+
         // Filling device and vring features VMM supports.
         let mut avail_features = 1 << VIRTIO_BLK_F_SEG_MAX
             | 1 << VIRTIO_BLK_F_RO
@@ -61,46 +64,16 @@ impl Blk {
             avail_features |= 1 << VIRTIO_BLK_F_MQ;
         }
 
-        let mut vhost_user_blk = Master::connect(&vu_cfg.socket, num_queues as u64)
-            .map_err(Error::VhostUserCreateMaster)?;
-
-        // Set vhost-user owner.
-        vhost_user_blk
-            .set_owner()
-            .map_err(Error::VhostUserSetOwner)?;
-
-        // Get features from backend, do negotiation to get a feature collection which
-        // both VMM and backend support.
-        let backend_features = vhost_user_blk
-            .get_features()
-            .map_err(Error::VhostUserGetFeatures)?;
-        let acked_features = avail_features & backend_features;
-        // Set features back is required by the vhost crate mechanism, since the
-        // later vhost call will check if features is filled in master before execution.
-        vhost_user_blk
-            .set_features(acked_features)
-            .map_err(Error::VhostUserSetFeatures)?;
-
         let avail_protocol_features = VhostUserProtocolFeatures::CONFIG
             | VhostUserProtocolFeatures::MQ
             | VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS
             | VhostUserProtocolFeatures::REPLY_ACK;
-        let acked_protocol_features =
-            if acked_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits() != 0 {
-                let backend_protocol_features = vhost_user_blk
-                    .get_protocol_features()
-                    .map_err(Error::VhostUserGetProtocolFeatures)?;
 
-                let acked_protocol_features = avail_protocol_features & backend_protocol_features;
+        let (acked_features, acked_protocol_features) = negotiate_features_vhost_user(
-
+            &mut vhost_user_blk,
-                vhost_user_blk
+            avail_features,
-                    .set_protocol_features(acked_protocol_features)
+            avail_protocol_features,
-                    .map_err(Error::VhostUserSetProtocolFeatures)?;
+        )?;
-
-                acked_protocol_features.bits()
-            } else {
-                0
-            };
 
         let backend_num_queues =
             if acked_protocol_features & VhostUserProtocolFeatures::MQ.bits() != 0 {

virtio-devices/src/vhost_user/fs.rs

@@ -2,7 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use super::vu_common_ctrl::{
-    add_memory_region, reset_vhost_user, setup_vhost_user, update_mem_table,
+    add_memory_region, negotiate_features_vhost_user, reset_vhost_user, setup_vhost_user,
+    update_mem_table,
 };
 use super::{Error, Result};
 use crate::seccomp_filters::{get_seccomp_filter, Thread};
@@ -26,7 +27,6 @@ use vhost::vhost_user::message::{
 use vhost::vhost_user::{
     HandlerResult, Master, MasterReqHandler, VhostUserMaster, VhostUserMasterReqHandler,
 };
-use vhost::VhostBackend;
 use virtio_bindings::bindings::virtio_ring::{
     VIRTIO_RING_F_EVENT_IDX, VIRTIO_RING_F_INDIRECT_DESC,
 };
@@ -312,23 +312,6 @@ impl Fs {
             | 1 << VIRTIO_RING_F_INDIRECT_DESC
             | VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits();
 
-        // Set vhost-user owner.
-        vhost_user_fs
-            .set_owner()
-            .map_err(Error::VhostUserSetOwner)?;
-
-        // Get features from backend, do negotiation to get a feature collection which
-        // both VMM and backend support.
-        let backend_features = vhost_user_fs
-            .get_features()
-            .map_err(Error::VhostUserGetFeatures)?;
-        let acked_features = avail_features & backend_features;
-        // Set features back is required by the vhost crate mechanism, since the
-        // later vhost call will check if features is filled in master before execution.
-        vhost_user_fs
-            .set_features(acked_features)
-            .map_err(Error::VhostUserSetFeatures)?;
-
         let mut avail_protocol_features = VhostUserProtocolFeatures::MQ
             | VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS
             | VhostUserProtocolFeatures::REPLY_ACK;
@@ -338,22 +321,11 @@ impl Fs {
             avail_protocol_features |= slave_protocol_features;
         }
 
-        let acked_protocol_features =
+        let (acked_features, acked_protocol_features) = negotiate_features_vhost_user(
-            if acked_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits() != 0 {
+            &mut vhost_user_fs,
-                let backend_protocol_features = vhost_user_fs
+            avail_features,
-                    .get_protocol_features()
+            avail_protocol_features,
-                    .map_err(Error::VhostUserGetProtocolFeatures)?;
+        )?;
-
-                let acked_protocol_features = avail_protocol_features & backend_protocol_features;
-
-                vhost_user_fs
-                    .set_protocol_features(acked_protocol_features)
-                    .map_err(Error::VhostUserSetProtocolFeatures)?;
-
-                acked_protocol_features.bits()
-            } else {
-                0
-            };
 
         let backend_num_queues =
             if acked_protocol_features & VhostUserProtocolFeatures::MQ.bits() != 0 {

virtio-devices/src/vhost_user/net.rs

@@ -91,41 +91,15 @@ impl Net {
                 .map_err(Error::VhostUserCreateMaster)?
         };
 
-        vhost_user_net
-            .set_owner()
-            .map_err(Error::VhostUserSetOwner)?;
-
-        // Get features from backend, do negotiation to get a feature collection which
-        // both VMM and backend support.
-        let backend_features = vhost_user_net
-            .get_features()
-            .map_err(Error::VhostUserGetFeatures)?;
-        let acked_features = avail_features & backend_features;
-        // Set features back is required by the vhost crate mechanism, since the
-        // later vhost call will check if features is filled in master before execution.
-        vhost_user_net
-            .set_features(acked_features)
-            .map_err(Error::VhostUserSetFeatures)?;
-
         let avail_protocol_features = VhostUserProtocolFeatures::MQ
             | VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS
             | VhostUserProtocolFeatures::REPLY_ACK;
-        let acked_protocol_features =
-            if acked_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits() != 0 {
-                let backend_protocol_features = vhost_user_net
-                    .get_protocol_features()
-                    .map_err(Error::VhostUserGetProtocolFeatures)?;
 
-                let acked_protocol_features = avail_protocol_features & backend_protocol_features;
+        let (acked_features, acked_protocol_features) = negotiate_features_vhost_user(
-
+            &mut vhost_user_net,
-                vhost_user_net
+            avail_features,
-                    .set_protocol_features(acked_protocol_features)
+            avail_protocol_features,
-                    .map_err(Error::VhostUserSetProtocolFeatures)?;
+        )?;
-
-                acked_protocol_features.bits()
-            } else {
-                0
-            };
 
         // If the control queue feature has not been negotiated, let's decrease
         // the number of queues.
@@ -138,7 +112,7 @@ impl Net {
                 vhost_user_net
                     .get_queue_num()
                     .map_err(Error::VhostUserGetQueueMaxNum)? as usize
-            } else if backend_features & (1 << virtio_net::VIRTIO_NET_F_CTRL_VQ) != 0 {
+            } else if acked_features & (1 << virtio_net::VIRTIO_NET_F_CTRL_VQ) != 0 {
                 DEFAULT_QUEUE_NUMBER + 1
             } else {
                 DEFAULT_QUEUE_NUMBER

virtio-devices/src/vhost_user/vu_common_ctrl.rs

@@ -8,6 +8,7 @@ use std::convert::TryInto;
 use std::os::unix::io::AsRawFd;
 use std::sync::Arc;
 use std::vec::Vec;
+use vhost::vhost_user::message::{VhostUserProtocolFeatures, VhostUserVirtioFeatures};
 use vhost::vhost_user::{Master, VhostUserMaster};
 use vhost::{VhostBackend, VhostUserMemoryRegionInfo, VringConfigData};
 use vm_memory::{
@@ -68,6 +69,42 @@ pub fn add_memory_region(vu: &mut Master, region: &Arc<GuestRegionMmap>) -> Resu
         .map_err(Error::VhostUserAddMemReg)
 }
 
+pub fn negotiate_features_vhost_user(
+    vu: &mut Master,
+    avail_features: u64,
+    avail_protocol_features: VhostUserProtocolFeatures,
+) -> Result<(u64, u64)> {
+    // Set vhost-user owner.
+    vu.set_owner().map_err(Error::VhostUserSetOwner)?;
+
+    // Get features from backend, do negotiation to get a feature collection which
+    // both VMM and backend support.
+    let backend_features = vu.get_features().map_err(Error::VhostUserGetFeatures)?;
+    let acked_features = avail_features & backend_features;
+    // Set features back is required by the vhost crate mechanism, since the
+    // later vhost call will check if features is filled in master before execution.
+    vu.set_features(acked_features)
+        .map_err(Error::VhostUserSetFeatures)?;
+
+    let acked_protocol_features =
+        if acked_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits() != 0 {
+            let backend_protocol_features = vu
+                .get_protocol_features()
+                .map_err(Error::VhostUserGetProtocolFeatures)?;
+
+            let acked_protocol_features = avail_protocol_features & backend_protocol_features;
+
+            vu.set_protocol_features(acked_protocol_features)
+                .map_err(Error::VhostUserSetProtocolFeatures)?;
+
+            acked_protocol_features.bits()
+        } else {
+            0
+        };
+
+    Ok((acked_features, acked_protocol_features))
+}
+
 pub fn setup_vhost_user(
     vu: &mut Master,
     mem: &GuestMemoryMmap,