devices, vmm: Add legacy CMOS device

Based off of crosvm revision b5237bbcf074eb30cf368a138c0835081e747d71
add a CMOS device. This environments that can't use KVM clock to get the
current time (e.g. Windows and EFI.)

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

Cargo.toml

@@ -31,10 +31,11 @@ path = "vhost_rs"
 features = ["vhost-user-slave"]
 
 [features]
-default = ["acpi", "pci"]
+default = ["acpi", "pci", "cmos"]
 acpi = ["vmm/acpi"]
 pci = ["vmm/pci_support"]
 mmio = ["vmm/mmio_support"]
+cmos = ["vmm/cmos"]
 
 # Integration tests require a special environment to run in
 integration_tests = []

devices/Cargo.toml

@@ -18,4 +18,5 @@ tempfile = "3.1.0"
 
 [features]
 default = []
-acpi = []
+acpi = []
+cmos = []

devices/src/legacy/cmos.rs

@@ -0,0 +1,115 @@
+// 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 libc::{gmtime_r, time, time_t, tm};
+use std::cmp::min;
+use std::mem;
+
+use crate::BusDevice;
+
+const INDEX_MASK: u8 = 0x7f;
+const INDEX_OFFSET: u64 = 0x0;
+const DATA_OFFSET: u64 = 0x1;
+const DATA_LEN: usize = 128;
+
+/// A CMOS/RTC device commonly seen on x86 I/O port 0x70/0x71.
+pub struct Cmos {
+    index: u8,
+    data: [u8; DATA_LEN],
+}
+
+impl Cmos {
+    /// Constructs a CMOS/RTC device with initial data.
+    /// `mem_below_4g` is the size of memory in bytes below the 32-bit gap.
+    /// `mem_above_4g` is the size of memory in bytes above the 32-bit gap.
+    pub fn new(mem_below_4g: u64, mem_above_4g: u64) -> Cmos {
+        let mut data = [0u8; DATA_LEN];
+
+        // Extended memory from 16 MB to 4 GB in units of 64 KB
+        let ext_mem = min(
+            0xFFFF,
+            mem_below_4g.saturating_sub(16 * 1024 * 1024) / (64 * 1024),
+        );
+        data[0x34] = ext_mem as u8;
+        data[0x35] = (ext_mem >> 8) as u8;
+
+        // High memory (> 4GB) in units of 64 KB
+        let high_mem = min(0x00FF_FFFF, mem_above_4g / (64 * 1024));
+        data[0x5b] = high_mem as u8;
+        data[0x5c] = (high_mem >> 8) as u8;
+        data[0x5d] = (high_mem >> 16) as u8;
+
+        Cmos { index: 0, data }
+    }
+}
+
+impl BusDevice for Cmos {
+    fn write(&mut self, _base: u64, offset: u64, data: &[u8]) {
+        if data.len() != 1 {
+            return;
+        }
+
+        match offset {
+            INDEX_OFFSET => self.index = data[0] & INDEX_MASK,
+            DATA_OFFSET => self.data[self.index as usize] = data[0],
+            o => panic!("bad write offset on CMOS device: {}", o),
+        }
+    }
+
+    fn read(&mut self, _base: u64, offset: u64, data: &mut [u8]) {
+        fn to_bcd(v: u8) -> u8 {
+            assert!(v < 100);
+            ((v / 10) << 4) | (v % 10)
+        }
+
+        if data.len() != 1 {
+            return;
+        }
+
+        data[0] = match offset {
+            INDEX_OFFSET => self.index,
+            DATA_OFFSET => {
+                let seconds;
+                let minutes;
+                let hours;
+                let week_day;
+                let day;
+                let month;
+                let year;
+                // The time and gmtime_r calls are safe as long as the structs they are given are
+                // large enough, and neither of them fail. It is safe to zero initialize the tm
+                // struct because it contains only plain data.
+                unsafe {
+                    let mut tm: tm = mem::zeroed();
+                    let mut now: time_t = 0;
+                    time(&mut now as *mut _);
+                    gmtime_r(&now, &mut tm as *mut _);
+                    // The following lines of code are safe but depend on tm being in scope.
+                    seconds = tm.tm_sec;
+                    minutes = tm.tm_min;
+                    hours = tm.tm_hour;
+                    week_day = tm.tm_wday + 1;
+                    day = tm.tm_mday;
+                    month = tm.tm_mon + 1;
+                    year = tm.tm_year;
+                };
+                match self.index {
+                    0x00 => to_bcd(seconds as u8),
+                    0x02 => to_bcd(minutes as u8),
+                    0x04 => to_bcd(hours as u8),
+                    0x06 => to_bcd(week_day as u8),
+                    0x07 => to_bcd(day as u8),
+                    0x08 => to_bcd(month as u8),
+                    0x09 => to_bcd((year % 100) as u8),
+                    0x32 => to_bcd(((year + 1900) / 100) as u8),
+                    _ => {
+                        // self.index is always guaranteed to be in range via INDEX_MASK.
+                        self.data[(self.index & INDEX_MASK) as usize]
+                    }
+                }
+            }
+            o => panic!("bad read offset on CMOS device: {}", o),
+        }
+    }
+}

devices/src/legacy/mod.rs

@@ -5,8 +5,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE-BSD-3-Clause file.
 
+#[cfg(feature = "cmos")]
+mod cmos;
 mod i8042;
 mod serial;
 
+#[cfg(feature = "cmos")]
+pub use self::cmos::Cmos;
 pub use self::i8042::I8042Device;
 pub use self::serial::Serial;

vmm/Cargo.toml

@@ -9,6 +9,7 @@ default = []
 acpi = ["acpi_tables","devices/acpi", "arch/acpi"]
 pci_support = ["pci", "vfio", "vm-virtio/pci_support"]
 mmio_support = ["vm-virtio/mmio_support"]
+cmos = ["devices/cmos"]
 
 [dependencies]
 acpi_tables = { path = "../acpi_tables", optional = true }

vmm/src/device_manager.rs

@@ -370,7 +370,22 @@ impl DeviceManager {
             .io
             .insert(i8042.clone(), 0x61, 0x4)
             .map_err(DeviceManagerError::BusError)?;
+        #[cfg(feature = "cmos")]
+        {
+            use vm_memory::GuestMemory;
+            let mem_size = vm_info.memory.as_ref().read().unwrap().end_addr().0 + 1;
+            let mem_below_4g = std::cmp::min(arch::layout::MEM_32BIT_RESERVED_START.0, mem_size);
+            let mem_above_4g = mem_size.saturating_sub(arch::layout::RAM_64BIT_START.0);
 
+            let cmos = Arc::new(Mutex::new(devices::legacy::Cmos::new(
+                mem_below_4g,
+                mem_above_4g,
+            )));
+            buses
+                .io
+                .insert(cmos.clone(), 0x70, 0x2)
+                .map_err(DeviceManagerError::BusError)?;
+        }
         #[cfg(feature = "acpi")]
         {
             let acpi_device = Arc::new(Mutex::new(devices::AcpiShutdownDevice::new(