vmm: fall back to GICv2 if GICv3 is not supported

The SoC in some popular boards (namely, the RPi family) doesn't support
an architected vGIC, which is required for requesting KVM the
instantiation of a GICv3. To relieve the users from having to configure
the gic version manually, try first to instantiate a GICv3, and fall
back to a GICv2 if it fails.

Signed-off-by: Sergio Lopez <[email protected]>

Author: slp

src/devices/src/legacy/kvmgicv3.rs

@@ -8,7 +8,7 @@ use crate::legacy::gic::GICDevice;
 use crate::legacy::irqchip::IrqChipT;
 use crate::Error as DeviceError;
 
-use kvm_ioctls::{DeviceFd, VmFd};
+use kvm_ioctls::{DeviceFd, Error, VmFd};
 use utils::eventfd::EventFd;
 
 const KVM_VGIC_V3_BASE_SIZE: u64 = 0x0001_0000;
@@ -27,7 +27,7 @@ pub struct KvmGicV3 {
 }
 
 impl KvmGicV3 {
-    pub fn new(vm: &VmFd, vcpu_count: u64) -> Self {
+    pub fn new(vm: &VmFd, vcpu_count: u64) -> Result<Self, Error> {
         let dist_size = KVM_VGIC_V3_BASE_SIZE;
         let dist_addr = arch::MMIO_MEM_START - dist_size;
         let redist_size = 2 * dist_size;
@@ -39,23 +39,23 @@ impl KvmGicV3 {
             fd: 0,
             flags: 0,
         };
-        let device_fd = vm.create_device(&mut gic_device).unwrap();
+        let device_fd = vm.create_device(&mut gic_device)?;
 
         let attr = kvm_bindings::kvm_device_attr {
             group: kvm_bindings::KVM_DEV_ARM_VGIC_GRP_ADDR,
             attr: u64::from(kvm_bindings::KVM_VGIC_V3_ADDR_TYPE_DIST),
             addr: &dist_addr as *const u64 as u64,
             flags: 0,
         };
-        device_fd.set_device_attr(&attr).unwrap();
+        device_fd.set_device_attr(&attr)?;
 
         let attr = kvm_bindings::kvm_device_attr {
             group: kvm_bindings::KVM_DEV_ARM_VGIC_GRP_ADDR,
             attr: u64::from(kvm_bindings::KVM_VGIC_V3_ADDR_TYPE_REDIST),
             addr: &redists_addr as *const u64 as u64,
             flags: 0,
         };
-        device_fd.set_device_attr(&attr).unwrap();
+        device_fd.set_device_attr(&attr)?;
 
         let nr_irqs: u32 = arch::aarch64::layout::IRQ_MAX - arch::aarch64::layout::IRQ_BASE + 1;
         let nr_irqs_ptr = &nr_irqs as *const u32;
@@ -65,21 +65,21 @@ impl KvmGicV3 {
             addr: nr_irqs_ptr as u64,
             flags: 0,
         };
-        device_fd.set_device_attr(&attr).unwrap();
+        device_fd.set_device_attr(&attr)?;
 
         let attr = kvm_bindings::kvm_device_attr {
             group: kvm_bindings::KVM_DEV_ARM_VGIC_GRP_CTRL,
             attr: u64::from(kvm_bindings::KVM_DEV_ARM_VGIC_CTRL_INIT),
             addr: 0,
             flags: 0,
         };
-        device_fd.set_device_attr(&attr).unwrap();
+        device_fd.set_device_attr(&attr)?;
 
-        Self {
+        Ok(Self {
             _device_fd: device_fd,
             properties: [dist_addr, dist_size, redists_addr, redists_size],
             vcpu_count,
-        }
+        })
     }
 }
 

src/vmm/src/builder.rs

@@ -30,8 +30,6 @@ use crate::vmm_config::external_kernel::{ExternalKernel, KernelFormat};
 use crate::vmm_config::net::NetBuilder;
 #[cfg(all(target_os = "linux", target_arch = "riscv64"))]
 use devices::legacy::KvmAia;
-#[cfg(all(target_os = "linux", target_arch = "aarch64"))]
-use devices::legacy::KvmGicV3;
 #[cfg(target_arch = "x86_64")]
 use devices::legacy::KvmIoapic;
 use devices::legacy::Serial;
@@ -42,6 +40,8 @@ use devices::legacy::{GicV3, HvfGicV3};
 #[cfg(target_arch = "x86_64")]
 use devices::legacy::{IoApic, IrqChipT};
 use devices::legacy::{IrqChip, IrqChipDevice};
+#[cfg(all(target_os = "linux", target_arch = "aarch64"))]
+use devices::legacy::{KvmGicV2, KvmGicV3};
 use devices::virtio::{port_io, MmioTransport, PortDescription, VirtioDevice, Vsock};
 
 #[cfg(feature = "tee")]
@@ -837,10 +837,18 @@ pub fn build_microvm(
         )
         .map_err(StartMicrovmError::Internal)?;
 
-        intc = Arc::new(Mutex::new(IrqChipDevice::new(Box::new(KvmGicV3::new(
-            vm.fd(),
-            vm_resources.vm_config().vcpu_count.unwrap() as u64,
-        )))));
+        intc = {
+            // The SoC in some popular boards (namely, the RPi family) doesn't support an
+            // architected vGIC, which is required for requesting KVM the instantiation of a
+            // GICv3. To relieve the users from having to configure the gic version manually,
+            // try first to instantiate a GICv3, and fall back to a GICv2 if it fails.
+            let vcpu_count = vm_resources.vm_config().vcpu_count.unwrap() as u64;
+            let gic = match KvmGicV3::new(vm.fd(), vcpu_count) {
+                Ok(gicv3) => IrqChipDevice::new(Box::new(gicv3)),
+                Err(_) => IrqChipDevice::new(Box::new(KvmGicV2::new(vm.fd(), vcpu_count))),
+            };
+            Arc::new(Mutex::new(gic))
+        };
 
         attach_legacy_devices(
             &vm,