Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping

[Andrew Cooper]

On 28/06/16 17:47, Vitaly Kuznetsov wrote:
> @@ -1808,6 +1822,8 @@ static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
>  	int cpu = (long)hcpu;
>  	switch (action) {
>  	case CPU_UP_PREPARE:
> +		/* vLAPIC_ID == Xen's vCPU_ID * 2 for HVM guests */
> +		per_cpu(xen_vcpu_id, cpu) = cpu_physical_id(cpu) / 2;

Please do not assume or propagate this brokenness.  It is incorrect in
the general case, and I will be fixing in the hypervisor in due course.

Always read the APIC_ID from the LAPIC, per regular hardware.

~Andrew