Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets an INIT

Gleb Natapov
2013-03-10T11:46:46Z

On Sat, Mar 09, 2013 at 07:48:33AM +0100, Paolo Bonzini wrote:
> After receiving an INIT signal (either via the local APIC, or through
> KVM_SET_MP_STATE), the bootstrap processor should reset immediately
> and start execution at 0xfffffff0. Also, SIPIs have no effect on the
> bootstrap processor. However, KVM currently does not differentiate
> between the BSP and APs.
>
Userspace is capable of resetting vcpu by itself, so adding code to
handle KVM_SET_MP_STATE(INIT) looks unnecessary to me. I think the
simple patch below (not tested) should handle INIT for in-kernel irq chip
and userspace does not need special handling for cpu reset. It already
knows how to reset cpu on system_reset, so reseting only cpus should not
be different.

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 02b51dd..6cb3c21 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -731,7 +731,9 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
case APIC_DM_INIT:
if (!trig_mode || level) {
result = 1;
- vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ vcpu->arch.mp_state = kvm_vcpu_is_bsp(vcpu) ?
+ KVM_MP_STATE_SIPI_RECEIVED :
+ KVM_MP_STATE_INIT_RECEIVED;
kvm_make_request(KVM_REQ_EVENT, vcpu);
kvm_vcpu_kick(vcpu);
} else {
--
Gleb.