Inflight I/O: Implement missing traits

This commit implements the get and set inflight fd members of the
VhostUserSlaveReqHandlerMut trait, which is used to pass inflight
I/O queue tracking regions as memfds.

Fixes #14.

Signed-off-by: Harshavardhan Unnibhavi <[email protected]>

Author: harshanavkis

src/lib.rs

@@ -7,30 +7,32 @@
 #[macro_use]
 extern crate log;
 
-use std::error;
 use std::fs::File;
 use std::io;
 use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
 use std::os::unix::prelude::IntoRawFd;
 use std::result;
 use std::sync::{Arc, Mutex, RwLock};
 use std::thread;
+use std::{error, mem};
 use vhost::vhost_user::message::{
-    VhostUserConfigFlags, VhostUserMemoryRegion, VhostUserProtocolFeatures,
+    DescStatePacked, DescStateSplit, QueueRegionPacked, QueueRegionSplit, VhostUserConfigFlags,
+    VhostUserInflight, VhostUserMemoryRegion, VhostUserProtocolFeatures,
     VhostUserSingleMemoryRegion, VhostUserVirtioFeatures, VhostUserVringAddrFlags,
     VhostUserVringState,
 };
 use vhost::vhost_user::{
     Error as VhostUserError, Listener, Result as VhostUserResult, SlaveFsCacheReq, SlaveListener,
     VhostUserSlaveReqHandlerMut,
 };
+use virtio_bindings::bindings::virtio_net::VIRTIO_F_RING_PACKED;
 use virtio_bindings::bindings::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
+use virtio_queue::Queue;
 use vm_memory::guest_memory::FileOffset;
 use vm_memory::{
     GuestAddress, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryMmap, GuestRegionMmap,
     MmapRegion,
 };
-use virtio_queue::Queue;
 use vmm_sys_util::eventfd::EventFd;
 
 const MAX_MEM_SLOTS: u64 = 32;
@@ -453,6 +455,7 @@ struct VhostUserHandler<S: VhostUserBackend> {
     atomic_mem: GuestMemoryAtomic<GuestMemoryMmap>,
     vrings: Vec<Arc<RwLock<Vring>>>,
     worker_threads: Vec<thread::JoinHandle<VringWorkerResult<()>>>,
+    inflight_file: Option<File>,
 }
 
 impl<S: VhostUserBackend> VhostUserHandler<S> {
@@ -536,6 +539,7 @@ impl<S: VhostUserBackend> VhostUserHandler<S> {
             atomic_mem,
             vrings,
             worker_threads,
+            inflight_file: None,
         })
     }
 
@@ -948,16 +952,56 @@ impl<S: VhostUserBackend> VhostUserSlaveReqHandlerMut for VhostUserHandler<S> {
 
     fn get_inflight_fd(
         &mut self,
-        _inflight: &vhost::vhost_user::message::VhostUserInflight,
-    ) -> VhostUserResult<(vhost::vhost_user::message::VhostUserInflight, File)> {
-        // Assume the backend hasn't negotiated the inflight feature; it
-        // wouldn't be correct for the backend to do so, as we don't (yet)
-        // provide a way for it to handle such requests.
-        Err(VhostUserError::InvalidOperation)
+        inflight: &VhostUserInflight,
+    ) -> VhostUserResult<(VhostUserInflight, File)> {
+        let inflight_queue_region = unsafe {
+            libc::syscall(
+                libc::SYS_memfd_create,
+                &std::ffi::CString::new("inflight-region").unwrap(),
+                libc::MFD_CLOEXEC,
+            )
+        };
+
+        self.inflight_file = Some(unsafe { File::from_raw_fd(inflight_queue_region as RawFd) });
+
+        let virtio_features = self.get_features().unwrap();
+        let total_mmap_size;
+        let queue_region_size;
+        let descr_state_size;
+        if virtio_features & (1 << VIRTIO_F_RING_PACKED) == 0 {
+            // Use descriptor and queue states for split virtqueues
+            queue_region_size = mem::size_of::<QueueRegionSplit>();
+            descr_state_size = mem::size_of::<DescStateSplit>();
+        } else {
+            // Use descriptor and queue states for packed virtqueues
+            queue_region_size = mem::size_of::<QueueRegionPacked>();
+            descr_state_size = mem::size_of::<DescStatePacked>();
+        }
+
+        total_mmap_size = (queue_region_size + descr_state_size * inflight.queue_size as usize)
+            * inflight.num_queues as usize;
+
+        unsafe { libc::ftruncate(inflight_queue_region as i32, total_mmap_size as i64) };
+
+        Ok((
+            VhostUserInflight {
+                mmap_size: total_mmap_size as u64,
+                mmap_offset: 0,
+                num_queues: inflight.num_queues,
+                queue_size: inflight.queue_size,
+            },
+            unsafe { File::from_raw_fd(inflight_queue_region as RawFd) },
+        ))
     }
 
-    fn set_inflight_fd(&mut self, _inflight: &vhost::vhost_user::message::VhostUserInflight, _file: File) -> VhostUserResult<()> {
-        Err(VhostUserError::InvalidOperation)
+    fn set_inflight_fd(
+        &mut self,
+        _inflight: &VhostUserInflight,
+        file: File,
+    ) -> VhostUserResult<()> {
+        self.inflight_file = Some(file);
+
+        Ok(())
     }
 }