Re: [PATCH v6 03/39] KVM: arm64: Return early from kvm_finalize_sys_regs() if guest has run

Jonathan Cameron
2026-03-19T10:31:19Z

On Tue, 17 Mar 2026 11:40:44 +0000
Sascha Bischoff <Sascha.Bischoff@arm.com> wrote:

> If the guest has already run, we have no business finalizing the
> system register state - it is too late. Therefore, check early and
> bail if the VM has already run.
Given it isn't in the scope below, might be worth calling out that
this is skipping kvm_init_nv_sysregs() So on non NV setups isn't
changing anything but on those it's indeed skipping setup of system
registers.

Seems correct to me, but is this a fix? So should it have a fixes tag?

>
> Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
> ---
> arch/arm64/kvm/sys_regs.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 0acd10e50aaba..42c84b7900ff5 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -5659,11 +5659,14 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu)
>
> guard(mutex)(&kvm->arch.config_lock);
>
> + if (kvm_vm_has_ran_once(kvm))
> + return 0;
> +
> /*
> * This hacks into the ID registers, so only perform it when the
> * first vcpu runs, or the kvm_set_vm_id_reg() helper will scream.
> */
> - if (!irqchip_in_kernel(kvm) && !kvm_vm_has_ran_once(kvm)) {
> + if (!irqchip_in_kernel(kvm)) {
> u64 val;
>
> val = kvm_read_vm_id_reg(kvm, SYS_ID_AA64PFR0_EL1) & ~ID_AA64PFR0_EL1_GIC;