KVM: arm64: Relax invariance of KVM_ARM_VCPU_POWER_OFF

Allow the value of KVM_ARM_VCPU_POWER_OFF to differ between calls to
KVM_ARM_VCPU_INIT. Userspace can already change the state of the vCPU
through the KVM_SET_MP_STATE ioctl, so making the bit invariant seems
needlessly restrictive.

Link: https://lore.kernel.org/r/20230609190054.1542113-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index d5298054a8edfb978b27949ad32424e0a4d9fb25..a9c18f45df3fcf923772d486bbb189b23957b20e 100644 (file)
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1236,8 +1236,19 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
 static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
                                         struct kvm_vcpu_init *init)
 {
+       bool power_off = false;
        int ret;
 
+       /*
+        * Treat the power-off vCPU feature as ephemeral. Clear the bit to avoid
+        * reflecting it in the finalized feature set, thus limiting its scope
+        * to a single KVM_ARM_VCPU_INIT call.
+        */
+       if (init->features[0] & KVM_ARM_VCPU_POWER_OFF) {
+               init->features[0] &= ~KVM_ARM_VCPU_POWER_OFF;
+               power_off = true;
+       }
+
        ret = kvm_vcpu_set_target(vcpu, init);
        if (ret)
                return ret;
@@ -1266,7 +1277,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
         */
        spin_lock(&vcpu->arch.mp_state_lock);
 
-       if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features))
+       if (power_off)
                __kvm_arm_vcpu_power_off(vcpu);
        else
                WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE);