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

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Message-ID: <20130310114646.GM11223@redhat.com>
Date:	Sun, 10 Mar 2013 13:46:46 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	mtosatti@...hat.com, jan.kiszka@...mens.com
Subject: Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets an
 INIT

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.
--
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