From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756796AbaCQRIw (ORCPT ); Mon, 17 Mar 2014 13:08:52 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:16483 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754655AbaCQRIu (ORCPT ); Mon, 17 Mar 2014 13:08:50 -0400 Message-ID: <53272CA1.3000609@oracle.com> Date: Mon, 17 Mar 2014 13:10:57 -0400 From: Boris Ostrovsky User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 MIME-Version: 1.0 To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com CC: Boris Ostrovsky , konrad.wilk@oracle.com, david.vrabel@citrix.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/xen: Disable APIC PM for Xen PV guests References: <1393900821-6182-1-git-send-email-boris.ostrovsky@oracle.com> In-Reply-To: <1393900821-6182-1-git-send-email-boris.ostrovsky@oracle.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/03/2014 09:40 PM, Boris Ostrovsky wrote: > Xen PV guests support only few APIC registers and writes to > unsupported registers result in WARN_ONs. Most APIC accesses in these > guests have been eliminated; however, lapic_suspend/resume are still > called (on 32-bit kernels). > > We can disable APIC power management in xen_smp_prepare_boot_cpu() > (which is called after APIC has been initialized). This touches generic APIC code so x86 maintainers' review would be appreciated. Thanks. -boris > Signed-off-by: Boris Ostrovsky > --- > arch/x86/include/asm/apic.h | 2 ++ > arch/x86/kernel/apic/apic.c | 6 ++++++ > arch/x86/xen/smp.c | 4 ++++ > 3 files changed, 12 insertions(+) > > > An alternative could be to add another op to stuct apic. The advantage would be > the fact that we never have a window of time when APIC PM is enabled. The downside > is having yet another op (of which there are already plenty). > > We could also avoid loading lapic_syscore_ops but I couldn't think of a good way > to figure out when not to do it. > > > > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h > index 1d2091a..1f100f2 100644 > --- a/arch/x86/include/asm/apic.h > +++ b/arch/x86/include/asm/apic.h > @@ -687,6 +687,8 @@ extern int default_cpu_present_to_apicid(int mps_cpu); > extern int default_check_phys_apicid_present(int phys_apicid); > #endif > > +extern void apic_pm_deactivate(void); > + > #endif /* CONFIG_X86_LOCAL_APIC */ > extern void irq_enter(void); > extern void irq_exit(void); > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index 7f26c9a..60607b3 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -2424,6 +2424,11 @@ static void apic_pm_activate(void) > apic_pm_state.active = 1; > } > > +void apic_pm_deactivate(void) > +{ > + apic_pm_state.active = 0; > +} > + > static int __init init_lapic_sysfs(void) > { > /* XXX: remove suspend/resume procs if !apic_pm_state.active? */ > @@ -2439,6 +2444,7 @@ core_initcall(init_lapic_sysfs); > #else /* CONFIG_PM */ > > static void apic_pm_activate(void) { } > +void apic_pm_deactivate(void) { } > > #endif /* CONFIG_PM */ > > diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c > index a18eadd..33115d8 100644 > --- a/arch/x86/xen/smp.c > +++ b/arch/x86/xen/smp.c > @@ -298,6 +298,10 @@ static void __init xen_smp_prepare_boot_cpu(void) > > xen_filter_cpu_maps(); > xen_setup_vcpu_info_placement(); > + > +#ifdef CONFIG_X86_LOCAL_APIC > + apic_pm_deactivate(); > +#endif > } > /* > * The alternative logic (which patches the unlock/lock) runs before