Re: [PATCH] KVM: Adding 'else' to reduce checking.

Vitaly Kuznetsov
2020-01-16T08:27:45Z

Haiwei Li <lihaiwei.kernel@gmail.com> writes:

> From 4e19436679a97e3cee73b4ae613ff91580c721d2 Mon Sep 17 00:00:00 2001
> From: Haiwei Li <lihaiwei@tencent.com>
> Date: Thu, 16 Jan 2020 13:51:03 +0800
> Subject: [PATCH] Adding 'else' to reduce checking.
>
> These two conditions are in conflict, adding 'else' to reduce checking.
>
> Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
> ---
> arch/x86/kvm/lapic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 679692b..ef5802f 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1573,7 +1573,7 @@ static void
> kvm_apic_inject_pending_timer_irqs(struct kvm_lapic *apic)
> kvm_apic_local_deliver(apic, APIC_LVTT);
> if (apic_lvtt_tscdeadline(apic))
> ktimer->tscdeadline = 0;
> - if (apic_lvtt_oneshot(apic)) {
> + else if (apic_lvtt_oneshot(apic)) {
> ktimer->tscdeadline = 0;
> ktimer->target_expiration = 0;
> }

I bet the compiler will generate the exact same code
(apic_lvtt_tscdeadline() and apic_lvtt_oneshot() are inlines), however,
I think your patch is still worthy: 'else' makes it obvious it's either
one or another and not both.

One nitpick: coding style requires braces even for single statements in
case other branches require them so in your case it should now be:

if (apic_lvtt_tscdeadline(apic)) {
ktimer->tscdeadline = 0;
} else if (apic_lvtt_oneshot(apic)) {
ktimer->tscdeadline = 0;
ktimer->target_expiration = 0;
}

With that,

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly