vfio_pci: add support for runtime power management

Allow devices to perform runtime power management via
VFIO_DEVICE_FEATURE IOCTL.

BUG=b:194390621
TEST=host's VFIO_DEVICE_FEATURE can be triggered from guest

Change-Id: Id649a1e5fe317dfb315f841a152ec8b81fab8e7c
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3822004
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Victor Ding <victording@chromium.org>

devices/src/pci/vfio_pci.rs

@@ -2026,12 +2026,24 @@ impl PciDevice for VfioPciDevice {
         0
     }
 
-    fn write_virtual_config_register(&mut self, reg_idx: usize, _value: u32) {
-        warn!(
-            "{} write unsupported register {}",
-            self.debug_label(),
-            reg_idx
-        )
+    fn write_virtual_config_register(&mut self, reg_idx: usize, value: u32) {
+        match reg_idx {
+            0 => {
+                match value {
+                    0 => {
+                        let _ = self.device.pm_low_power_enter();
+                    }
+                    _ => {
+                        let _ = self.device.pm_low_power_exit();
+                    }
+                };
+            }
+            _ => warn!(
+                "{} write unsupported register {}",
+                self.debug_label(),
+                reg_idx
+            ),
+        };
     }
 
     fn read_bar(&mut self, addr: u64, data: &mut [u8]) {

devices/src/vfio.rs

@@ -104,6 +104,10 @@ pub enum VfioError {
     VfioIrqMask(Error),
     #[error("failed to unmask vfio deviece's irq: {0}")]
     VfioIrqUnmask(Error),
+    #[error("failed to enter vfio deviece's low power state: {0}")]
+    VfioPmLowPowerEnter(Error),
+    #[error("failed to exit vfio deviece's low power state: {0}")]
+    VfioPmLowPowerExit(Error),
     #[error("container dones't support VfioType1V2 IOMMU driver type")]
     VfioType1V2,
 }
@@ -849,6 +853,34 @@ impl VfioDevice {
         &self.name
     }
 
+    /// enter the device's low power state
+    pub fn pm_low_power_enter(&self) -> Result<()> {
+        let mut device_feature = vec_with_array_field::<vfio_device_feature, u8>(0);
+        device_feature[0].argsz = mem::size_of::<vfio_device_feature>() as u32;
+        device_feature[0].flags = VFIO_DEVICE_FEATURE_SET | VFIO_DEVICE_FEATURE_LOW_POWER_ENTRY;
+        // Safe as we are the owner of self and power_management which are valid value
+        let ret = unsafe { ioctl_with_ref(&self.dev, VFIO_DEVICE_FEATURE(), &device_feature[0]) };
+        if ret < 0 {
+            Err(VfioError::VfioPmLowPowerEnter(get_error()))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// exit the device's low power state
+    pub fn pm_low_power_exit(&self) -> Result<()> {
+        let mut device_feature = vec_with_array_field::<vfio_device_feature, u8>(0);
+        device_feature[0].argsz = mem::size_of::<vfio_device_feature>() as u32;
+        device_feature[0].flags = VFIO_DEVICE_FEATURE_SET | VFIO_DEVICE_FEATURE_LOW_POWER_EXIT;
+        // Safe as we are the owner of self and power_management which are valid value
+        let ret = unsafe { ioctl_with_ref(&self.dev, VFIO_DEVICE_FEATURE(), &device_feature[0]) };
+        if ret < 0 {
+            Err(VfioError::VfioPmLowPowerExit(get_error()))
+        } else {
+            Ok(())
+        }
+    }
+
     /// Enable vfio device's irq and associate Irqfd Event with device.
     /// When MSIx is enabled, multi vectors will be supported, and vectors starting from subindex to subindex +
     /// descriptors length will be assigned with irqfd in the descriptors array.

seccomp/x86_64/vfio_device.policy

@@ -4,8 +4,11 @@
 
 @include /usr/share/policy/crosvm/common_device.policy
 
-# VFIO_DEVICE_SET_IRQS, VFIO_IOMMU_MAP/UNMAP_DMA
-ioctl: arg1 == 0x3B6E || arg1 == 0x3B71 || arg1 == 0x3B72
+# 0x3B6E: VFIO_DEVICE_SET_IRQS
+# 0x3B71: VFIO_IOMMU_MAP_DMA
+# 0x3B72: VFIO_IOMMU_UNMAP_DMA
+# 0x3B75: VFIO_DEVICE_FEATURE
+ioctl: arg1 == 0x3B6E || arg1 == 0x3B71 || arg1 == 0x3B72 || arg1 == 0x3B75
 open: return ENOENT
 openat: return ENOENT
 pread64: 1

vfio_sys/src/lib.rs

@@ -43,6 +43,7 @@ ioctl_io_nr!(VFIO_IOMMU_MAP_DMA, VFIO_TYPE, VFIO_BASE + 13);
 ioctl_io_nr!(VFIO_IOMMU_UNMAP_DMA, VFIO_TYPE, VFIO_BASE + 14);
 ioctl_io_nr!(VFIO_IOMMU_ENABLE, VFIO_TYPE, VFIO_BASE + 15);
 ioctl_io_nr!(VFIO_IOMMU_DISABLE, VFIO_TYPE, VFIO_BASE + 16);
+ioctl_io_nr!(VFIO_DEVICE_FEATURE, VFIO_TYPE, VFIO_BASE + 17);
 
 ioctl_io_nr!(
     PLAT_IRQ_FORWARD_SET,

vfio_sys/src/vfio.rs

@@ -147,6 +147,9 @@ pub const VFIO_DEVICE_FEATURE_GET: u32 = 65536;
 pub const VFIO_DEVICE_FEATURE_SET: u32 = 131072;
 pub const VFIO_DEVICE_FEATURE_PROBE: u32 = 262144;
 pub const VFIO_DEVICE_FEATURE_PCI_VF_TOKEN: u32 = 0;
+pub const VFIO_DEVICE_FEATURE_LOW_POWER_ENTRY: u32 = 3;
+pub const VFIO_DEVICE_FEATURE_LOW_POWER_ENTRY_WITH_WAKEUP: u32 = 4;
+pub const VFIO_DEVICE_FEATURE_LOW_POWER_EXIT: u32 = 5;
 pub const VFIO_IOMMU_INFO_PGSIZES: u32 = 1;
 pub const VFIO_IOMMU_INFO_CAPS: u32 = 2;
 pub const VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE: u32 = 1;
@@ -390,6 +393,12 @@ pub struct vfio_device_feature {
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Clone)]
+pub struct vfio_device_low_power_entry_with_wakeup {
+    pub wakeup_eventfd: i32,
+    pub reserved: u32,
+}
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
 pub struct vfio_iommu_type1_info {
     pub argsz: u32,
     pub flags: u32,