Re: [PATCH 1/5] KVM: Reject attempts to lock all vCPUs if vCPU creation is in-progress

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Redundant manual check for vCPU creation left behind in ARM VGIC initialization.
--

commit 62db20a1fe5b1f9f44f668c005957e7cf68b7547
Author: Sean Christopherson <seanjc@google.com>

KVM: Reject attempts to lock all vCPUs if vCPU creation is in-progress

This commit updates KVM to reject attempts to lock all vCPUs while vCPU
creation is in progress by adding checks inside kvm_trylock_all_vcpus()
and kvm_lock_all_vcpus(). It also opportunistically drops existing manual
checks that precede or follow locking all vCPUs.

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 65eb26a0520d8..78cc090435be5 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1363,6 +1363,9 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
>  
>  	lockdep_assert_held(&kvm->lock);
>  
> +	if (kvm_is_vcpu_creation_in_progress(kvm))
> +		return -EBUSY;
> +

[Severity: Low]
Was the manual check in arch/arm64/kvm/vgic/vgic-init.c missed during the
cleanup of redundant in-progress vCPU creation checks?

The commit message notes that existing manual checks are being dropped, but
in kvm_vgic_create(), there is still a manual check immediately following the
kvm_trylock_all_vcpus() call:

arch/arm64/kvm/vgic/vgic-init.c:kvm_vgic_create() {
        ...
        ret = kvm_trylock_all_vcpus(kvm);
        if (ret)
                return ret;

        ret = -EBUSY;
        if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
                goto out_unlock;
        ...
}

Because this condition is now evaluated inside the preceding
kvm_trylock_all_vcpus() call, this manual check in kvm_vgic_create() appears
to be left as dead code and will never evaluate to true.

>  	kvm_for_each_vcpu(i, vcpu, kvm)
>  		if (!mutex_trylock_nest_lock(&vcpu->mutex, &kvm->lock))
>  			goto out_unlock;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260914181223.289061-1-seanjc@google.com?part=1