fix: power off vcpus only during startup

Vcpus should be in power off state during kernel boot,
but during snapshot restore we do not need to power them off
even thought kvm does not complain. To do this we stop applying
the `KVM_ARM_VCPU_POWER_OFF` to the `kvi` during restore.
Also if we need to store `kvi` in the state, do this before adding
`KVM_ARM_VCPU_POWER_OFF` to it, so that during restore `kvi`
will not have `KVM_ARM_VCPU_POWER_OFF` set.

Signed-off-by: Egor Lazarchuk <[email protected]>

Author: ShadowCurse

src/vmm/src/vstate/vcpu/aarch64.rs

@@ -129,30 +129,32 @@ impl KvmVcpu {
         vm_fd: &VmFd,
         vcpu_features: &[VcpuFeatures],
     ) -> Result<(), KvmVcpuError> {
-        let mut kvi = Self::default_kvi(vm_fd, self.index)?;
+        let mut kvi = Self::default_kvi(vm_fd)?;
 
         for feature in vcpu_features.iter() {
             let index = feature.index as usize;
             kvi.features[index] = feature.bitmap.apply(kvi.features[index]);
         }
 
-        self.init_vcpu(&kvi)?;
-        self.finalize_vcpu(&kvi)?;
-
         self.kvi = if !vcpu_features.is_empty() {
             Some(kvi)
         } else {
             None
         };
 
+        // Non-boot cpus are powered off initially.
+        if 0 < self.index {
+            kvi.features[0] |= 1 << kvm_bindings::KVM_ARM_VCPU_POWER_OFF;
+        }
+
+        self.init_vcpu(&kvi)?;
+        self.finalize_vcpu(&kvi)?;
+
         Ok(())
     }
 
     /// Creates default kvi struct based on vcpu index.
-    pub fn default_kvi(
-        vm_fd: &VmFd,
-        index: u8,
-    ) -> Result<kvm_bindings::kvm_vcpu_init, KvmVcpuError> {
+    pub fn default_kvi(vm_fd: &VmFd) -> Result<kvm_bindings::kvm_vcpu_init, KvmVcpuError> {
         let mut kvi: kvm_bindings::kvm_vcpu_init = kvm_bindings::kvm_vcpu_init::default();
         // This reads back the kernel's preferred target type.
         vm_fd
@@ -161,11 +163,6 @@ impl KvmVcpu {
         // We already checked that the capability is supported.
         kvi.features[0] |= 1 << kvm_bindings::KVM_ARM_VCPU_PSCI_0_2;
 
-        // Non-boot cpus are powered off initially.
-        if index > 0 {
-            kvi.features[0] |= 1 << kvm_bindings::KVM_ARM_VCPU_POWER_OFF;
-        }
-
         Ok(kvi)
     }
 
@@ -185,7 +182,7 @@ impl KvmVcpu {
     pub fn restore_state(&mut self, vm_fd: &VmFd, state: &VcpuState) -> Result<(), KvmVcpuError> {
         let kvi = match state.kvi {
             Some(kvi) => kvi,
-            None => Self::default_kvi(vm_fd, self.index)?,
+            None => Self::default_kvi(vm_fd)?,
         };
         self.kvi = state.kvi;