src: add vhost-user-blk backend

Create a vhost-user-blk backend using vhost-user-backend and following
the conventions established by the existing vhost-user-net
implementation.

This backend is based on https://github.com/slp/vhost-user-backend,
but a bit simplified, making it closer to the original implementation
in Firecracker. The main features missing are EVENT_IDX, support for
asynchronous I/O and multiqueue, but it's still fully functional and
provides a good starting point for evolving it into a more complete
implementation.

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

Cargo.lock

@@ -174,6 +174,7 @@ dependencies = [
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "net_gen 0.1.0",
  "net_util 0.1.0",
+ "qcow 0.1.0",
  "ssh2 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "vhost_rs 0.1.0",

Cargo.toml

@@ -12,6 +12,7 @@ libc = "0.2.65"
 log = { version = "0.4.8", features = ["std"] }
 net_gen = { path = "net_gen" }
 net_util = { path = "net_util" }
+qcow = { path = "qcow" }
 vhost_user_backend = { path = "vhost_user_backend"}
 virtio-bindings = "0.1.0"
 vmm = { path = "vmm" }

src/bin/vhost_user_blk.rs

@@ -0,0 +1,300 @@
+// Copyright 2019 Red Hat, Inc. All Rights Reserved.
+//
+// Portions Copyright 2019 Intel Corporation. All Rights Reserved.
+//
+// Portions Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
+//
+// SPDX-License-Identifier: (Apache-2.0 AND BSD-3-Clause)
+
+#[macro_use(crate_version, crate_authors)]
+extern crate clap;
+extern crate log;
+extern crate vhost_rs;
+extern crate vhost_user_backend;
+extern crate vm_virtio;
+
+use clap::{App, Arg};
+use epoll;
+use log::*;
+use std::fs::File;
+use std::fs::OpenOptions;
+use std::io::Read;
+use std::io::{Seek, SeekFrom, Write};
+use std::mem;
+use std::path::PathBuf;
+use std::process;
+use std::slice;
+use std::sync::{Arc, RwLock};
+use std::vec::Vec;
+
+use qcow::{self, ImageType, QcowFile};
+
+use vhost_rs::vhost_user::message::*;
+use vhost_user_backend::{VhostUserBackend, VhostUserDaemon, Vring, VringWorker};
+
+use virtio_bindings::bindings::virtio_blk::*;
+use vm_memory::{Bytes, GuestMemoryError, GuestMemoryMmap};
+use vm_virtio::block::{build_disk_image_id, Request};
+
+const QUEUE_SIZE: usize = 1024;
+const NUM_QUEUES: usize = 1;
+const SECTOR_SHIFT: u8 = 9;
+const SECTOR_SIZE: u64 = (0x01 as u64) << SECTOR_SHIFT;
+const BLK_SIZE: u32 = 512;
+
+trait DiskFile: Read + Seek + Write + Send + Sync {}
+impl<D: Read + Seek + Write + Send + Sync> DiskFile for D {}
+
+pub type Result<T> = std::result::Result<T, Error>;
+pub type VhostUserBackendResult<T> = std::result::Result<T, std::io::Error>;
+
+#[derive(Debug)]
+pub enum Error {
+    /// Failed to detect image type.
+    DetectImageType,
+    /// Bad memory address.
+    GuestMemory(GuestMemoryError),
+    /// Can't open image file.
+    OpenImage,
+    /// Failed to parse image parameter.
+    ParseImageParam,
+    /// Failed to parse sock parameter.
+    ParseSockParam,
+}
+
+struct VhostUserBlkBackend {
+    mem: Option<GuestMemoryMmap>,
+    vring_worker: Option<Arc<VringWorker>>,
+    disk_image: Box<dyn DiskFile>,
+    disk_image_id: Vec<u8>,
+    disk_nsectors: u64,
+    config: virtio_blk_config,
+}
+
+impl VhostUserBlkBackend {
+    pub fn new(image_path: String) -> Result<Self> {
+        let raw_img: File = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .open(&image_path)
+            .unwrap();
+
+        let image_id = build_disk_image_id(&PathBuf::from(&image_path));
+        let image_type = qcow::detect_image_type(&raw_img).unwrap();
+        let mut image = match image_type {
+            ImageType::Raw => Box::new(vm_virtio::RawFile::new(raw_img)) as Box<dyn DiskFile>,
+            ImageType::Qcow2 => Box::new(QcowFile::from(raw_img).unwrap()) as Box<dyn DiskFile>,
+        };
+
+        let nsectors = (image.seek(SeekFrom::End(0)).unwrap() as u64) / SECTOR_SIZE;
+        let mut config = virtio_blk_config::default();
+
+        config.capacity = nsectors;
+        config.blk_size = BLK_SIZE;
+        config.size_max = 65535;
+        config.seg_max = 128 - 2;
+        config.min_io_size = 1;
+        config.opt_io_size = 1;
+        config.num_queues = 1;
+
+        Ok(VhostUserBlkBackend {
+            mem: None,
+            vring_worker: None,
+            disk_image: image,
+            disk_image_id: image_id,
+            disk_nsectors: nsectors,
+            config,
+        })
+    }
+
+    pub fn process_queue(&mut self, vring: &mut Vring) -> bool {
+        let mut used_any = false;
+        let mem = match self.mem.as_ref() {
+            Some(m) => m,
+            None => return false,
+        };
+
+        while let Some(head) = vring.mut_queue().iter(mem).next() {
+            debug!("got an element in the queue");
+            let len;
+            match Request::parse(&head, mem) {
+                Ok(request) => {
+                    debug!("element is a valid request");
+                    let status = match request.execute(
+                        &mut self.disk_image,
+                        self.disk_nsectors,
+                        mem,
+                        &self.disk_image_id,
+                    ) {
+                        Ok(l) => {
+                            len = l;
+                            VIRTIO_BLK_S_OK
+                        }
+                        Err(e) => {
+                            len = 1;
+                            e.status()
+                        }
+                    };
+                    mem.write_obj(status, request.status_addr).unwrap();
+                }
+                Err(err) => {
+                    error!("failed to parse available descriptor chain: {:?}", err);
+                    len = 0;
+                }
+            }
+            vring.mut_queue().add_used(mem, head.index, len);
+            used_any = true;
+        }
+
+        used_any
+    }
+}
+
+impl VhostUserBackend for VhostUserBlkBackend {
+    fn num_queues(&self) -> usize {
+        NUM_QUEUES
+    }
+
+    fn max_queue_size(&self) -> usize {
+        QUEUE_SIZE
+    }
+
+    fn features(&self) -> u64 {
+        1 << VIRTIO_BLK_F_MQ
+            | 1 << VIRTIO_F_VERSION_1
+            | VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits()
+    }
+
+    fn protocol_features(&self) -> VhostUserProtocolFeatures {
+        VhostUserProtocolFeatures::CONFIG
+    }
+
+    fn update_memory(&mut self, mem: GuestMemoryMmap) -> VhostUserBackendResult<()> {
+        self.mem = Some(mem);
+        Ok(())
+    }
+
+    fn handle_event(
+        &mut self,
+        device_event: u16,
+        evset: epoll::Events,
+        vrings: &[Arc<RwLock<Vring>>],
+    ) -> VhostUserBackendResult<bool> {
+        if evset != epoll::Events::EPOLLIN {
+            warn!("invalid events operation");
+            return Ok(false);
+        }
+
+        debug!("event received: {:?}", device_event);
+
+        let mut vring = vrings[0].write().unwrap();
+        if self.process_queue(&mut vring) {
+            debug!("signalling queue");
+            vring.signal_used_queue().unwrap();
+        }
+
+        Ok(false)
+    }
+
+    fn get_config(&self, _offset: u32, _size: u32) -> Vec<u8> {
+        // self.config is a statically allocated virtio_blk_config
+        let buf = unsafe {
+            slice::from_raw_parts(
+                &self.config as *const virtio_blk_config as *const _,
+                mem::size_of::<virtio_blk_config>(),
+            )
+        };
+
+        buf.to_vec()
+    }
+}
+
+pub struct VhostUserBlkBackendConfig<'a> {
+    pub image: &'a str,
+    pub sock: &'a str,
+}
+
+impl<'a> VhostUserBlkBackendConfig<'a> {
+    pub fn parse(backend: &'a str) -> Result<Self> {
+        let params_list: Vec<&str> = backend.split(',').collect();
+
+        let mut image: &str = "";
+        let mut sock: &str = "";
+
+        for param in params_list.iter() {
+            if param.starts_with("image=") {
+                image = &param[6..];
+            } else if param.starts_with("sock=") {
+                sock = &param[5..];
+            }
+        }
+
+        if image.is_empty() {
+            return Err(Error::ParseImageParam);
+        }
+        if sock.is_empty() {
+            return Err(Error::ParseSockParam);
+        }
+
+        Ok(VhostUserBlkBackendConfig { image, sock })
+    }
+}
+
+fn main() {
+    let cmd_arguments = App::new("vhost-user-blk backend")
+        .version(crate_version!())
+        .author(crate_authors!())
+        .about("Launch a vhost-user-blk backend.")
+        .arg(
+            Arg::with_name("backend")
+                .long("backend")
+                .help(
+                    "Backend parameters \"image=<image_path>,\
+                     sock=<socket_path>\"",
+                )
+                .takes_value(true)
+                .min_values(1),
+        )
+        .get_matches();
+
+    let vhost_user_blk_backend = cmd_arguments.value_of("backend").unwrap();
+
+    let backend_config = match VhostUserBlkBackendConfig::parse(vhost_user_blk_backend) {
+        Ok(config) => config,
+        Err(e) => {
+            println!("Failed parsing parameters {:?}", e);
+            process::exit(1);
+        }
+    };
+
+    let blk_backend = Arc::new(RwLock::new(
+        VhostUserBlkBackend::new(backend_config.image.to_string()).unwrap(),
+    ));
+
+    debug!("blk_backend is created!\n");
+
+    let name = "vhost-user-blk-backend";
+    let mut blk_daemon = VhostUserDaemon::new(
+        name.to_string(),
+        backend_config.sock.to_string(),
+        blk_backend.clone(),
+    )
+    .unwrap();
+    debug!("blk_daemon is created!\n");
+
+    let vring_worker = blk_daemon.get_vring_worker();
+
+    blk_backend.write().unwrap().vring_worker = Some(vring_worker);
+
+    if let Err(e) = blk_daemon.start() {
+        println!(
+            "failed to start daemon for vhost-user-blk with error: {:?}\n",
+            e
+        );
+        process::exit(1);
+    }
+
+    blk_daemon.wait().unwrap();
+}