Re: [RFC PATCH 01/13] KVM: SVM: Add warning when encounter invalid APIC ID

[Maxim Levitsky]

On Sun, 2022-02-20 at 20:19 -0600, Suravee Suthikulpanit wrote:
> Current logic checks if avic_get_physical_id_entry() fails to
> get the entry, and return error. This could silently cause
> AVIC to fail to operate.  Therefore, add WARN_ON to help
> report this error.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> ---
>  arch/x86/kvm/svm/avic.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index f07956f15d3b..472445aaaf42 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -447,8 +447,10 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
>  
>  	old = avic_get_physical_id_entry(vcpu, vcpu->vcpu_id);
>  	new = avic_get_physical_id_entry(vcpu, id);
> -	if (!new || !old)
> +	if (!new || !old) {
> +		WARN_ON(1);
>  		return 1;
> +	}
>  
>  	/* We need to move physical_id_entry to new offset */
>  	*new = *old;

I about to purge all of this code, and disallow setting the apicid regardles
if x2apic, or plain xapic was used at least when AVIC is enabled.
I really hope for this to be accepted, so we won't need to fix this code.

Best regards,
	Maxim Levitsky