Re: [PATCH v3 07/14] KVM: x86: reset APIC ID when enabling LAPIC

Wanpeng Li
2016-08-02T13:29:58Z

2016-07-13 4:09 GMT+08:00 Radim Krčmář <rkrcmar@redhat.com>:
> APIC ID should be set to the initial APIC ID when enabling LAPIC.
> This only matters if the guest changes APIC ID. No sane OS does that.
>
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
> arch/x86/kvm/lapic.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 41089dbeeafc..0fce77fdbe91 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1720,9 +1720,10 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
>
> /* update jump label if enable bit changes */
> if ((old_value ^ value) & MSR_IA32_APICBASE_ENABLE) {
> - if (value & MSR_IA32_APICBASE_ENABLE)
> + if (value & MSR_IA32_APICBASE_ENABLE) {
> + kvm_apic_set_xapic_id(apic, vcpu->vcpu_id);
> static_key_slow_dec_deferred(&apic_hw_disabled);
> - else
> + } else
> static_key_slow_inc(&apic_hw_disabled.key);
> recalculate_apic_map(vcpu->kvm);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If we can drop this recalculate_apic_map() since it has already been
called by kvm_apic_set_xapic_id().

Regards,
Wanpeng Li