From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754428AbcBHPMc (ORCPT ); Mon, 8 Feb 2016 10:12:32 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34325 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753506AbcBHPMa (ORCPT ); Mon, 8 Feb 2016 10:12:30 -0500 Subject: Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do To: Bruce Rogers , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <1454539876-8310-1-git-send-email-brogers@suse.com> <1454539876-8310-2-git-send-email-brogers@suse.com> Cc: jan.kiszka@siemens.com, namit@cs.technion.ac.il From: Paolo Bonzini Message-ID: <56B8B057.5050900@redhat.com> Date: Mon, 8 Feb 2016 16:12:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <1454539876-8310-2-git-send-email-brogers@suse.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/02/2016 23:51, Bruce Rogers wrote: > The INIT IPI event handler special cases the boot-strap processor > (BSP) handling, avoiding the same mp state handling which is done for > the other (AP) processors. Debugging a linux guest usage scenario of > avoiding a reboot through the bios for a crash on any processor via eg: > kexec -p /boot/vmlinuz --initrd=/boot/initrd --append="$(cat /proc/cmdline)\ > maxcpus=1" led to identifying this change as the needed fix. > > With this change, an AP can now startup the BSP without error. > > Signed-off-by: Bruce Rogers > --- > arch/x86/kvm/lapic.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 36591fa..eda6bfb 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -2170,10 +2170,7 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu) > if (test_bit(KVM_APIC_INIT, &pe)) { > kvm_lapic_reset(vcpu, true); > kvm_vcpu_reset(vcpu, true); > - if (kvm_vcpu_is_bsp(apic->vcpu)) > - vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; > - else > - vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED; > + vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED; > } > if (test_bit(KVM_APIC_SIPI, &pe) && > vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) { > KVM_MP_STATE_INIT_RECEIVED is what Intel calls the "wait for SIPI" state. The BSP never gets a SIPI, it goes straight to 0xFFFFFFF0 instead. Can you explain the problem more in detail? Paolo