Re: [PATCH v4 5/5] x86: KVM: SEV: implement kvm_lock_all_vcpus and use it

Sean Christopherson
2025-05-02T20:57:15Z

On Wed, Apr 30, 2025, Maxim Levitsky wrote:
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 834f08dfa24c..9211b07b0565 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1392,6 +1392,31 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
> }
> EXPORT_SYMBOL_GPL(kvm_trylock_all_vcpus);
>
> +/*
> + * Lock all of the VM's vCPUs.
> + * Assumes that the kvm->lock is held.

Add a lockdep assertion instead of a comment.

> + * Returns -EINTR if the process is killed.
> + */
> +int kvm_lock_all_vcpus(struct kvm *kvm)
> +{
> + struct kvm_vcpu *vcpu;
> + unsigned long i, j;
> +
> + kvm_for_each_vcpu(i, vcpu, kvm)

Needs curly braces.

> + if (mutex_lock_killable_nest_lock(&vcpu->mutex, &kvm->lock))

I'd rather return mutex_lock_killable_nest_lock()'s error code verbatim. Then
the function comment can go away, because the only thing remaining would be:

/*
* Lock all of the VM's vCPUs.
/*

and that should be completely self-explanatory. E.g.

int kvm_lock_all_vcpus(struct kvm *kvm)
{
struct kvm_vcpu *vcpu;
unsigned long i, j;
int r;

lockdep_assert_held(&kvm->lock);

kvm_for_each_vcpu(i, vcpu, kvm) {
r = mutex_lock_killable_nest_lock(&vcpu->mutex, &kvm->lock);
if (r)
goto out_unlock;
}
return 0;

out_unlock:
kvm_for_each_vcpu(j, vcpu, kvm) {
if (i == j)
break;
mutex_unlock(&vcpu->mutex);
}
return r;
}
EXPORT_SYMBOL_GPL(kvm_lock_all_vcpus);