vfio_pci: add support for ACPI _DSM forwarding

Allow devices to host's ACPI _DSM via the recently proposed
VFIO_DEVICE_ACPI_DSM IOCTL

Co-authored-by: Xiong Zhang <xiong.y.zhang@intel.corp-partner.google.com>

BUG=b:194391459, b:289878032
TEST=host's ACPI _DSM method can be triggered from guest

Change-Id: I8de8cfbc85cdf6f9f15e53d4c5a4d4a3aa564ebd
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3822005
Reviewed-by: Grzegorz Jaszczyk <jaszczyk@google.com>
Commit-Queue: Grzegorz Jaszczyk <jaszczyk@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

devices/src/pci/vfio_pci.rs

@@ -2085,12 +2085,24 @@ impl PciDevice for VfioPciDevice {
     }
 
     fn read_virtual_config_register(&self, reg_idx: usize) -> u32 {
+        // HACK TODO:
+        // The results should be passed via shared memory (see `write_virtual_config_register`);
+        // HOWEVER, for not-yet-known reasons, Guest is unable to see the changes immediately
+        // even after `msync`. While the investigation is still ongoing, let's use this hack
+        // temporarily to unblock integration tests.
+        if reg_idx < 1024 {
+            if let Some(shm) = &self.vcfg_shm_mmap {
+                return shm
+                    .read_obj::<u32>(reg_idx * std::mem::size_of::<u32>())
+                    .expect("failed to read vcfg.");
+            }
+        }
         warn!(
-            "{} read unsupported register {}",
+            "{} read unsupported vcfg register {}",
             self.debug_label(),
             reg_idx
         );
-        0
+        0xFFFF_FFFF
     }
 
     fn write_virtual_config_register(&mut self, reg_idx: usize, value: u32) {
@@ -2113,8 +2125,22 @@ impl PciDevice for VfioPciDevice {
                     }
                 };
             }
+            1 => {
+                if let Some(shm) = &self.vcfg_shm_mmap {
+                    let mut args = [0u8; 4096];
+                    shm.read_slice(&mut args, 0)
+                        .expect("failed to read DSM Args.");
+                    let res = self
+                        .device
+                        .acpi_dsm(args.to_vec())
+                        .expect("failed to call DSM.");
+                    shm.write_slice(&res, 0)
+                        .expect("failed to write DSM result.");
+                    shm.msync().expect("failed to msync.");
+                }
+            }
             _ => warn!(
-                "{} write unsupported register {}",
+                "{} write unsupported vcfg register {}",
                 self.debug_label(),
                 reg_idx
             ),

devices/src/vfio.rs

@@ -43,6 +43,7 @@ use resources::Alloc;
 use resources::Error as ResourcesError;
 use sync::Mutex;
 use thiserror::Error;
+use vfio_sys::vfio::vfio_acpi_dsm;
 use vfio_sys::*;
 use vm_memory::MemoryRegionInformation;
 use zerocopy::AsBytes;
@@ -93,6 +94,8 @@ pub enum VfioError {
     Resources(ResourcesError),
     #[error("unknown vfio device type (flags: {0:#x})")]
     UnknownDeviceType(u32),
+    #[error("failed to call vfio device's ACPI _DSM: {0}")]
+    VfioAcpiDsm(Error),
     #[error(
         "vfio API version doesn't match with VFIO_API_VERSION defined in vfio_sys/src/vfio.rs"
     )]
@@ -947,6 +950,27 @@ impl VfioDevice {
         }
     }
 
+    /// call _DSM from the device's ACPI table
+    pub fn acpi_dsm(&self, args: Vec<u8>) -> Result<Vec<u8>> {
+        let count = args.len();
+        let mut dsm = vec_with_array_field::<vfio_acpi_dsm, u8>(count);
+        dsm[0].argsz = (mem::size_of::<vfio_acpi_dsm>() + count * mem::size_of::<u8>()) as u32;
+        dsm[0].padding = 0;
+        // Safe as we allocated enough space to hold args
+        unsafe {
+            dsm[0].args.as_mut_slice(count).clone_from_slice(&args);
+        }
+        // Safe as we are the owner of self and dsm which are valid value
+        let ret = unsafe { ioctl_with_mut_ref(&self.dev, VFIO_DEVICE_ACPI_DSM(), &mut dsm[0]) };
+        if ret < 0 {
+            Err(VfioError::VfioAcpiDsm(get_error()))
+        } else {
+            // Safe as we allocated enough space to hold args
+            let res = unsafe { dsm[0].args.as_slice(count) };
+            Ok(res.to_vec())
+        }
+    }
+
     /// 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.

jail/seccomp/x86_64/vfio_device.policy

@@ -8,7 +8,13 @@
 # 0x3B71: VFIO_IOMMU_MAP_DMA
 # 0x3B72: VFIO_IOMMU_UNMAP_DMA
 # 0x3B75: VFIO_DEVICE_FEATURE
-ioctl: arg1 == 0x3B6E || arg1 == 0x3B71 || arg1 == 0x3B72 || arg1 == 0x3B75
+# 0x3B76: VFIO_DEVICE_ACPI_DSM
+ioctl: arg1 == 0x3B6E || \
+       arg1 == 0x3B71 || \
+       arg1 == 0x3B72 || \
+       arg1 == 0x3B75 || \
+       arg1 == 0x3B76
+msync: 1
 open: return ENOENT
 openat: return ENOENT
 pread64: 1

vfio_sys/src/lib.rs

@@ -101,6 +101,7 @@ 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!(VFIO_DEVICE_ACPI_DSM, VFIO_TYPE, VFIO_BASE + 18);
 
 ioctl_io_nr!(
     PLAT_IRQ_FORWARD_SET,

vfio_sys/src/vfio.rs

@@ -613,3 +613,10 @@ pub struct vfio_iommu_spapr_tce_remove {
     pub flags: u32,
     pub start_addr: u64,
 }
+#[repr(C)]
+#[derive(Debug, Default)]
+pub struct vfio_acpi_dsm {
+    pub argsz: u32,
+    pub padding: u32,
+    pub args: __IncompleteArrayField<u8>,
+}