vmm: Add acpi table for fw_cfg device

This allows the fw_cfg device to be recognized by the guest linux
kernel. This becomes more relavnt in the following cl where I add
the option to load files into the guest via fw_cfg. The Linux kernel
already has a fw_cfg driver that will automatically load these files
under /sys when CONFIG_FW_CFG_SYSFS is enabled in the kernel config

For arm we must add fw_cfg to the devices tree

Signed-off-by: Alex Orozco <alexorozco@google.com>

arch/Cargo.toml

@@ -6,6 +6,7 @@ version = "0.1.0"
 
 [features]
 default = []
+fw_cfg = []
 kvm = ["hypervisor/kvm"]
 sev_snp = []
 tdx = []

arch/src/aarch64/fdt.rs

@@ -850,6 +850,21 @@ fn create_gpio_node<T: DeviceInfoForFdt + Clone + Debug>(
     Ok(())
 }
 
+// https://www.kernel.org/doc/Documentation/devicetree/bindings/arm/fw-cfg.txt
+#[cfg(feature = "fw_cfg")]
+fn create_fw_cfg_node<T: DeviceInfoForFdt + Clone + Debug>(
+    fdt: &mut FdtWriter,
+    dev_info: &T,
+) -> FdtWriterResult<()> {
+    // FwCfg node
+    let fw_cfg_node = fdt.begin_node(&format!("fw-cfg@{:x}", dev_info.addr()))?;
+    fdt.property("compatible", b"qemu,fw-cfg-mmio\0")?;
+    fdt.property_array_u64("reg", &[dev_info.addr(), dev_info.length()])?;
+    fdt.end_node(fw_cfg_node)?;
+
+    Ok(())
+}
+
 fn create_devices_node<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHasher>(
     fdt: &mut FdtWriter,
     dev_info: &HashMap<(DeviceType, String), T, S>,
@@ -865,6 +880,8 @@ fn create_devices_node<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::Buil
             DeviceType::Virtio(_) => {
                 ordered_virtio_device.push(info);
             }
+            #[cfg(feature = "fw_cfg")]
+            DeviceType::FwCfg => create_fw_cfg_node(fdt, info)?,
         }
     }
 

arch/src/lib.rs

@@ -155,6 +155,9 @@ pub enum DeviceType {
     /// Device Type: GPIO.
     #[cfg(target_arch = "aarch64")]
     Gpio,
+    /// Device Type: fw_cfg.
+    #[cfg(feature = "fw_cfg")]
+    FwCfg,
 }
 
 /// Default (smallest) memory page size for the supported architectures.

devices/Cargo.toml

@@ -44,6 +44,6 @@ arch = { path = "../arch" }
 
 [features]
 default = []
-fw_cfg = ["bitfield-struct", "linux-loader", "zerocopy"]
+fw_cfg = ["arch/fw_cfg", "bitfield-struct", "linux-loader", "zerocopy"]
 kvm = ["arch/kvm"]
 pvmemcontrol = []

devices/src/legacy/fw_cfg.rs

@@ -91,6 +91,8 @@ const FW_CFG_KNOWN_ITEMS: usize = 0x20;
 
 pub const FW_CFG_FILE_FIRST: u16 = 0x20;
 pub const FW_CFG_DMA_SIGNATURE: [u8; 8] = *b"QEMU CFG";
+// https://github.com/torvalds/linux/blob/master/include/uapi/linux/qemu_fw_cfg.h
+pub const FW_CFG_ACPI_ID: &str = "QEMU0002";
 // Reserved (must be enabled)
 const FW_CFG_F_RESERVED: u8 = 1 << 0;
 // DMA Toggle Bit (enabled by default)

vmm/src/device_manager.rs

@@ -53,6 +53,8 @@ use devices::gic;
 use devices::interrupt_controller::InterruptController;
 #[cfg(target_arch = "x86_64")]
 use devices::ioapic;
+#[cfg(all(feature = "fw_cfg", target_arch = "x86_64"))]
+use devices::legacy::fw_cfg::FW_CFG_ACPI_ID;
 #[cfg(target_arch = "aarch64")]
 use devices::legacy::Pl011;
 #[cfg(any(target_arch = "x86_64", target_arch = "riscv64"))]
@@ -1495,11 +1497,29 @@ impl DeviceManager {
         // default address for fw_cfg on arm via mmio
         // https://github.com/torvalds/linux/blob/master/drivers/firmware/qemu_fw_cfg.c#L27
         #[cfg(target_arch = "aarch64")]
-        self.address_manager
+        {
-            .mmio_bus
+            self.address_manager
-            .insert(fw_cfg.clone(), PORT_FW_CFG_BASE, PORT_FW_CFG_WIDTH)
+                .mmio_bus
-            .map_err(DeviceManagerError::ErrorAddingFwCfgToBus)?;
+                .insert(fw_cfg.clone(), PORT_FW_CFG_BASE, PORT_FW_CFG_WIDTH)
+                .map_err(DeviceManagerError::ErrorAddingFwCfgToBus)?;
 
+            let fw_cfg_irq = self
+                .address_manager
+                .allocator
+                .lock()
+                .unwrap()
+                .allocate_irq()
+                .unwrap();
+
+            self.id_to_dev_info.insert(
+                (DeviceType::FwCfg, "fw-cfg".to_string()),
+                MmioDeviceInfo {
+                    addr: PORT_FW_CFG_BASE,
+                    len: PORT_FW_CFG_WIDTH,
+                    irq: fw_cfg_irq,
+                },
+            );
+        }
         Ok(())
     }
 
@@ -5003,6 +5023,27 @@ impl Aml for DeviceManager {
         )
         .to_aml_bytes(sink);
 
+        #[cfg(all(feature = "fw_cfg", target_arch = "x86_64"))]
+        if self.fw_cfg.is_some() {
+            aml::Device::new(
+                "_SB_.FWCF".into(),
+                vec![
+                    &aml::Name::new("_HID".into(), &FW_CFG_ACPI_ID.to_string()),
+                    &aml::Name::new("_STA".into(), &0xB_usize),
+                    &aml::Name::new(
+                        "_CRS".into(),
+                        &aml::ResourceTemplate::new(vec![&aml::IO::new(
+                            PORT_FW_CFG_BASE as u16,
+                            PORT_FW_CFG_BASE as u16,
+                            0x01,
+                            PORT_FW_CFG_WIDTH as u8,
+                        )]),
+                    ),
+                ],
+            )
+            .to_aml_bytes(sink);
+        }
+
         // Serial device
         #[cfg(target_arch = "x86_64")]
         let serial_irq = 4;