[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/xen: Disable APIC PM for Xen PV guests
On 03/04/2014 05:25 AM, David Vrabel wrote: On 04/03/14 02:40, 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).Having looked at another APIC related problem recently, I wonder if Xen would be better served by having its own APIC driver instead of trying to piggy-back of some hardware one which doesn't do what we want. Possibly, although I don't think it will help with this particular issue since this patch is trying to address a problem in non-privileged guests. Such guests don't have ACPI enabled and so no APIC probing is done for them. -boris DavidSigned-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> --- 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.cindex 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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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