Re: [PATCH v2 2/2] KVM: LAPIC: Don't need to clear IPI delivery status in x2apic mode

From: Paolo Bonzini
Date: Tue Mar 31 2020 - 20:35:47 EST


On 01/04/20 02:19, Wanpeng Li wrote:
> - /* No delay here, so we always clear the pending bit */
> - val &= ~(1 << 12);
> + /* Immediately clear Delivery Status in xAPIC mode */
> + if (!apic_x2apic_mode(apic))
> + val &= ~(1 << 12);

This adds a conditional, and the old behavior was valid according to the
SDM: "software should not assume the value returned by reading the ICR
is the last written value".

Paolo