vm-virtio: Add MMIO transport

Derived from the crosvm code at 5656c124af2bb956dba19e409a269ca588c685e3
and adapted to work within cloud-hypervisor:

Main differences:

* Interrupt handling is done via a VirtioInterrupt turned into a
devices::Interrupt
* GuestMemory -> GuestMemoryMmap
* Differences in read/write for BusDevice
* Different crates for EventFd and GuestAddress

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vm-virtio/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 [features]
 default = []
 pci_support = ["pci"]
+mmio_support = []
 
 [dependencies]
 byteorder = "1.3.2"

vm-virtio/src/transport/mmio.rs

@@ -0,0 +1,249 @@
+// Copyright 2017 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, RwLock};
+
+use byteorder::{ByteOrder, LittleEndian};
+use libc::EFD_NONBLOCK;
+
+use crate::{
+    Queue, VirtioDevice, VirtioInterrupt, VirtioInterruptType, DEVICE_ACKNOWLEDGE, DEVICE_DRIVER,
+    DEVICE_DRIVER_OK, DEVICE_FAILED, DEVICE_FEATURES_OK, INTERRUPT_STATUS_CONFIG_CHANGED,
+    INTERRUPT_STATUS_USED_RING,
+};
+use devices::{BusDevice, Interrupt};
+use vm_memory::{GuestAddress, GuestMemoryMmap};
+use vmm_sys_util::{errno::Result, eventfd::EventFd};
+
+const VENDOR_ID: u32 = 0;
+
+const MMIO_MAGIC_VALUE: u32 = 0x7472_6976;
+const MMIO_VERSION: u32 = 2;
+
+/// Implements the
+/// [MMIO](http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-1090002)
+/// transport for virtio devices.
+///
+/// This requires 3 points of installation to work with a VM:
+///
+/// 1. Mmio reads and writes must be sent to this device at what is referred to here as MMIO base.
+/// 1. `Mmio::queue_evts` must be installed at `virtio::NOTIFY_REG_OFFSET` offset from the MMIO
+/// base. Each event in the array must be signaled if the index is written at that offset.
+/// 1. `Mmio::interrupt_evt` must signal an interrupt that the guest driver is listening to when it
+/// is written to.
+///
+/// Typically one page (4096 bytes) of MMIO address space is sufficient to handle this transport
+/// and inner virtio device.
+pub struct MmioDevice {
+    device: Box<dyn VirtioDevice>,
+    device_activated: bool,
+
+    features_select: u32,
+    acked_features_select: u32,
+    queue_select: u32,
+    interrupt_status: Arc<AtomicUsize>,
+    interrupt_cb: Option<Arc<VirtioInterrupt>>,
+    driver_status: u32,
+    config_generation: u32,
+    queues: Vec<Queue>,
+    queue_evts: Vec<EventFd>,
+    mem: Option<Arc<RwLock<GuestMemoryMmap>>>,
+}
+
+impl MmioDevice {
+    /// Constructs a new MMIO transport for the given virtio device.
+    pub fn new(
+        mem: Arc<RwLock<GuestMemoryMmap>>,
+        device: Box<dyn VirtioDevice>,
+    ) -> Result<MmioDevice> {
+        let mut queue_evts = Vec::new();
+        for _ in device.queue_max_sizes().iter() {
+            queue_evts.push(EventFd::new(EFD_NONBLOCK)?)
+        }
+        let queues = device
+            .queue_max_sizes()
+            .iter()
+            .map(|&s| Queue::new(s))
+            .collect();
+        Ok(MmioDevice {
+            device,
+            device_activated: false,
+            features_select: 0,
+            acked_features_select: 0,
+            queue_select: 0,
+            interrupt_status: Arc::new(AtomicUsize::new(0)),
+            interrupt_cb: None,
+
+            driver_status: 0,
+            config_generation: 0,
+            queues,
+            queue_evts,
+            mem: Some(mem),
+        })
+    }
+
+    /// Gets the list of queue events that must be triggered whenever the VM writes to
+    /// `virtio::NOTIFY_REG_OFFSET` past the MMIO base. Each event must be triggered when the
+    /// value being written equals the index of the event in this list.
+    pub fn queue_evts(&self) -> &[EventFd] {
+        self.queue_evts.as_slice()
+    }
+
+    fn is_driver_ready(&self) -> bool {
+        let ready_bits = DEVICE_ACKNOWLEDGE | DEVICE_DRIVER | DEVICE_DRIVER_OK | DEVICE_FEATURES_OK;
+        self.driver_status == ready_bits && self.driver_status & DEVICE_FAILED == 0
+    }
+
+    fn are_queues_valid(&self) -> bool {
+        if let Some(mem) = self.mem.as_ref() {
+            self.queues.iter().all(|q| q.is_valid(&mem.read().unwrap()))
+        } else {
+            false
+        }
+    }
+
+    fn with_queue<U, F>(&self, d: U, f: F) -> U
+    where
+        F: FnOnce(&Queue) -> U,
+    {
+        match self.queues.get(self.queue_select as usize) {
+            Some(queue) => f(queue),
+            None => d,
+        }
+    }
+
+    fn with_queue_mut<F: FnOnce(&mut Queue)>(&mut self, f: F) -> bool {
+        if let Some(queue) = self.queues.get_mut(self.queue_select as usize) {
+            f(queue);
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn assign_interrupt(&mut self, interrupt: Box<dyn Interrupt>) {
+        let interrupt_status = self.interrupt_status.clone();
+        let cb = Arc::new(Box::new(
+            move |int_type: &VirtioInterruptType, _queue: Option<&Queue>| {
+                let status = match int_type {
+                    VirtioInterruptType::Config => INTERRUPT_STATUS_CONFIG_CHANGED,
+                    VirtioInterruptType::Queue => INTERRUPT_STATUS_USED_RING,
+                };
+                interrupt_status.fetch_or(status as usize, Ordering::SeqCst);
+
+                interrupt.deliver()
+            },
+        ) as VirtioInterrupt);
+
+        self.interrupt_cb = Some(cb);
+    }
+}
+
+impl BusDevice for MmioDevice {
+    fn read(&mut self, _base: u64, offset: u64, data: &mut [u8]) {
+        match offset {
+            0x00..=0xff if data.len() == 4 => {
+                let v = match offset {
+                    0x0 => MMIO_MAGIC_VALUE,
+                    0x04 => MMIO_VERSION,
+                    0x08 => self.device.device_type(),
+                    0x0c => VENDOR_ID, // vendor id
+                    0x10 => {
+                        self.device.features(self.features_select)
+                            | if self.features_select == 1 { 0x1 } else { 0x0 }
+                    }
+                    0x34 => self.with_queue(0, |q| u32::from(q.get_max_size())),
+                    0x44 => self.with_queue(0, |q| q.ready as u32),
+                    0x60 => self.interrupt_status.load(Ordering::SeqCst) as u32,
+                    0x70 => self.driver_status,
+                    0xfc => self.config_generation,
+                    _ => {
+                        warn!("unknown virtio mmio register read: 0x{:x}", offset);
+                        return;
+                    }
+                };
+                LittleEndian::write_u32(data, v);
+            }
+            0x100..=0xfff => self.device.read_config(offset - 0x100, data),
+            _ => {
+                warn!(
+                    "invalid virtio mmio read: 0x{:x}:0x{:x}",
+                    offset,
+                    data.len()
+                );
+            }
+        };
+    }
+
+    fn write(&mut self, _base: u64, offset: u64, data: &[u8]) {
+        fn hi(v: &mut GuestAddress, x: u32) {
+            *v = (*v & 0xffff_ffff) | (u64::from(x) << 32)
+        }
+
+        fn lo(v: &mut GuestAddress, x: u32) {
+            *v = (*v & !0xffff_ffff) | u64::from(x)
+        }
+
+        let mut mut_q = false;
+        match offset {
+            0x00..=0xff if data.len() == 4 => {
+                let v = LittleEndian::read_u32(data);
+                match offset {
+                    0x14 => self.features_select = v,
+                    0x20 => self.device.ack_features(self.acked_features_select, v),
+                    0x24 => self.acked_features_select = v,
+                    0x30 => self.queue_select = v,
+                    0x38 => mut_q = self.with_queue_mut(|q| q.size = v as u16),
+                    0x44 => mut_q = self.with_queue_mut(|q| q.ready = v == 1),
+                    0x64 => {
+                        self.interrupt_status
+                            .fetch_and(!(v as usize), Ordering::SeqCst);
+                    }
+                    0x70 => self.driver_status = v,
+                    0x80 => mut_q = self.with_queue_mut(|q| lo(&mut q.desc_table, v)),
+                    0x84 => mut_q = self.with_queue_mut(|q| hi(&mut q.desc_table, v)),
+                    0x90 => mut_q = self.with_queue_mut(|q| lo(&mut q.avail_ring, v)),
+                    0x94 => mut_q = self.with_queue_mut(|q| hi(&mut q.avail_ring, v)),
+                    0xa0 => mut_q = self.with_queue_mut(|q| lo(&mut q.used_ring, v)),
+                    0xa4 => mut_q = self.with_queue_mut(|q| hi(&mut q.used_ring, v)),
+                    _ => {
+                        warn!("unknown virtio mmio register write: 0x{:x}", offset);
+                        return;
+                    }
+                }
+            }
+            0x100..=0xfff => return self.device.write_config(offset - 0x100, data),
+            _ => {
+                warn!(
+                    "invalid virtio mmio write: 0x{:x}:0x{:x}",
+                    offset,
+                    data.len()
+                );
+                return;
+            }
+        }
+
+        if self.device_activated && mut_q {
+            warn!("virtio queue was changed after device was activated");
+        }
+
+        if !self.device_activated && self.is_driver_ready() && self.are_queues_valid() {
+            if let Some(interrupt_cb) = self.interrupt_cb.take() {
+                if self.mem.is_some() {
+                    let mem = self.mem.as_ref().unwrap().clone();
+                    self.device
+                        .activate(
+                            mem,
+                            interrupt_cb,
+                            self.queues.clone(),
+                            self.queue_evts.split_off(0),
+                        )
+                        .expect("Failed to activate device");
+                    self.device_activated = true;
+                }
+            }
+        }
+    }
+}

vm-virtio/src/transport/mod.rs

@@ -10,3 +10,10 @@ mod pci_device;
 pub use pci_common_config::VirtioPciCommonConfig;
 #[cfg(feature = "pci_support")]
 pub use pci_device::VirtioPciDevice;
+
+#[cfg(feature = "mmio_support")]
+mod mmio;
+#[cfg(feature = "mmio_support")]
+pub use mmio::MmioDevice;
+#[cfg(feature = "mmio_support")]
+pub const NOTIFY_REG_OFFSET: u32 = 0x50;