Re: [PATCH 1/2] KVM: arm64: vgic-v4: Don't allocate vPEs for a GICv2 VM

[Oliver Upton]

On Mon, Oct 26, 2026 at 03:26:38PM +0000, Fuad Tabba wrote:
> KVM can run a GICv2 VM on a GICv4.0 host whose CPU interface supports
> legacy operation.

I'm pretty sure there's no IP out there that has GICv4.0 and legacy
mode...

> Such a VM has no LPIs and never uses vPEs, so
> vgic_supports_direct_irqs() is false for it and kvm_vgic_dist_destroy()
> never tears them down. However, userspace can still create an ITS for
> it. Once the vgic is initialised, vgic_its_create() calls
> vgic_v4_init(), which allocates the vPEs and requests a doorbell IRQ for
> each vCPU. They're then never freed, and each doorbell handler stays
> registered with a vCPU that's freed with the VM.
> 
> Only allocate vPEs for a GICv3 VM.
> 
> Fixes: 74fe55dc9ab77 ("KVM: arm/arm64: GICv4: Add init/teardown of the per-VM vPE irq domain")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>
> ---
>  arch/arm64/kvm/vgic/vgic-v4.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
> index ed236f083f0d7..a01de4de608a6 100644
> --- a/arch/arm64/kvm/vgic/vgic-v4.c
> +++ b/arch/arm64/kvm/vgic/vgic-v4.c
> @@ -248,7 +248,7 @@ int vgic_v4_init(struct kvm *kvm)
>  
>  	lockdep_assert_held(&kvm->arch.config_lock);
>  
> -	if (!kvm_vgic_global_state.has_gicv4)
> +	if (!kvm_vgic_global_state.has_gicv4 || dist->vgic_model != KVM_DEV_TYPE_ARM_VGIC_V3)

use vgic_is_v3() instead

Thanks,
Oliver

>  		return 0; /* Nothing to see here... move along. */
>  
>  	if (dist->its_vm.vpes)
> -- 
> 2.47.3
> 
>