1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

// Copyright 2021 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

mod sys;

use anyhow::anyhow;
use anyhow::bail;
use anyhow::Context;
use cros_async::Executor;
use serde::Deserialize;
use serde::Serialize;
pub use sys::start_device as run_block_device;
pub use sys::Options;
use vm_memory::GuestMemory;
use vmm_vhost::message::*;

use crate::virtio;
use crate::virtio::block::asynchronous::BlockAsync;
use crate::virtio::vhost::user::device::handler::DeviceRequestHandler;
use crate::virtio::vhost::user::device::handler::VhostUserDevice;
use crate::virtio::vhost::user::device::VhostUserDeviceBuilder;
use crate::virtio::Interrupt;
use crate::virtio::VirtioDevice;

const NUM_QUEUES: u16 = 16;

struct BlockBackend {
    inner: Box<BlockAsync>,

    avail_features: u64,
    acked_features: u64,
    acked_protocol_features: VhostUserProtocolFeatures,
}

#[derive(Serialize, Deserialize)]
struct BlockBackendSnapshot {
    acked_features: u64,
    // `avail_features` and `acked_protocol_features` don't need to be snapshotted, but they are
    // to be used to make sure that the proper features are used on `restore`.
    avail_features: u64,
    acked_protocol_features: u64,
}

impl VhostUserDeviceBuilder for BlockAsync {
    fn build(self: Box<Self>, _ex: &Executor) -> anyhow::Result<Box<dyn vmm_vhost::Backend>> {
        let avail_features = self.features() | 1 << VHOST_USER_F_PROTOCOL_FEATURES;
        let backend = BlockBackend {
            inner: self,
            avail_features,
            acked_features: 0,
            acked_protocol_features: VhostUserProtocolFeatures::empty(),
        };
        let handler = DeviceRequestHandler::new(backend);
        Ok(Box::new(handler))
    }
}

impl VhostUserDevice for BlockBackend {
    fn max_queue_num(&self) -> usize {
        NUM_QUEUES as usize
    }

    fn features(&self) -> u64 {
        self.avail_features
    }

    fn ack_features(&mut self, value: u64) -> anyhow::Result<()> {
        let unrequested_features = value & !self.avail_features;
        if unrequested_features != 0 {
            bail!("invalid features are given: {:#x}", unrequested_features);
        }

        self.acked_features |= value;

        Ok(())
    }

    fn acked_features(&self) -> u64 {
        self.acked_features
    }

    fn protocol_features(&self) -> VhostUserProtocolFeatures {
        VhostUserProtocolFeatures::CONFIG
            | VhostUserProtocolFeatures::MQ
            | VhostUserProtocolFeatures::BACKEND_REQ
    }

    fn ack_protocol_features(&mut self, features: u64) -> anyhow::Result<()> {
        let features = VhostUserProtocolFeatures::from_bits(features)
            .ok_or_else(|| anyhow!("invalid protocol features are given: {:#x}", features))?;
        let supported = self.protocol_features();
        self.acked_protocol_features = features & supported;
        Ok(())
    }

    fn acked_protocol_features(&self) -> u64 {
        self.acked_protocol_features.bits()
    }

    fn read_config(&self, offset: u64, data: &mut [u8]) {
        self.inner.read_config(offset, data)
    }

    fn reset(&mut self) {
        if let Err(e) = self.inner.reset() {
            base::error!("reset failed: {:#}", e);
        }
    }

    fn start_queue(
        &mut self,
        idx: usize,
        queue: virtio::Queue,
        mem: GuestMemory,
        doorbell: Interrupt,
    ) -> anyhow::Result<()> {
        self.inner.start_queue(idx, queue, mem, doorbell)
    }

    fn stop_queue(&mut self, idx: usize) -> anyhow::Result<virtio::Queue> {
        self.inner.stop_queue(idx)
    }

    fn stop_non_queue_workers(&mut self) -> anyhow::Result<()> {
        // TODO: This assumes that `reset` only stops workers which might not be true in the
        // future. Consider moving the `reset` code into a `stop_all_workers` method or, maybe,
        // make `stop_queue` implicitly stop a worker thread when there is no active queue.
        self.inner.reset()
    }

    fn snapshot(&self) -> anyhow::Result<Vec<u8>> {
        // The queue states are being snapshotted in the device handler.
        let serialized_bytes = serde_json::to_vec(&BlockBackendSnapshot {
            acked_features: self.acked_features,
            avail_features: self.avail_features,
            acked_protocol_features: self.acked_protocol_features.bits(),
        })
        .context("Failed to serialize BlockBackendSnapshot")?;

        Ok(serialized_bytes)
    }

    fn restore(&mut self, data: Vec<u8>) -> anyhow::Result<()> {
        let block_backend_snapshot: BlockBackendSnapshot =
            serde_json::from_slice(&data).context("Failed to deserialize BlockBackendSnapshot")?;
        anyhow::ensure!(
            self.avail_features == block_backend_snapshot.avail_features,
            "Vhost user block restored avail_features do not match. Live: {:?}, snapshot: {:?}",
            self.avail_features,
            block_backend_snapshot.avail_features,
        );
        anyhow::ensure!(
            self.acked_protocol_features.bits() == block_backend_snapshot.acked_protocol_features,
            "Vhost user block restored acked_protocol_features do not match. Live: {:?}, \
            snapshot: {:?}",
            self.acked_protocol_features,
            block_backend_snapshot.acked_protocol_features
        );
        self.acked_features = block_backend_snapshot.acked_features;
        Ok(())
    }
}