Messages in this thread | | | Date | Wed, 02 Dec 2015 18:30:59 +0100 | From | Sander Eikelenboom <> | Subject | Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. |
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On 2015-12-02 15:55, David Vrabel wrote: > On 28/11/15 15:47, Sander Eikelenboom wrote: >> genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 >> (rtc0) > > We shouldn't register an rtc_cmos device because its legacy irq > conflicts with the irq needed for hvc0. For a multi VCPU guest irq 8 > is > in use for the pv spinlocks and this gets requested first, preventing > the rtc device from probing. > > Does this patch fix it for you? > > David
It does, thanks.
Reported-and-tested-by: Sander Eikelenboom <linux@eikelenboom.it>
-- Sander
> 8<-------------------- > x86: rtc_cmos platform device requires legacy irqs > > Adding the rtc platform device when there are no legacy irqs (no > legacy PIC) causes a conflict with other devices that end up using the > same irq number. > > In a single VCPU PV guest we should have: > > /proc/interrupts: > CPU0 > 0: 4934 xen-percpu-virq timer0 > 1: 0 xen-percpu-ipi spinlock0 > 2: 0 xen-percpu-ipi resched0 > 3: 0 xen-percpu-ipi callfunc0 > 4: 0 xen-percpu-virq debug0 > 5: 0 xen-percpu-ipi callfuncsingle0 > 6: 0 xen-percpu-ipi irqwork0 > 7: 321 xen-dyn-event xenbus > 8: 90 xen-dyn-event hvc_console > ... > > But hvc_console cannot get its interrupt because it is already in use > by rtc0 and the console does not work. > > genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 > (rtc0) > > The rtc_cmos device requires a particular legacy irq so don't add it > if there are no legacy irqs. > > Signed-off-by: David Vrabel <david.vrabel@citrix.com> > --- > arch/x86/kernel/rtc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c > index cd96852..07c70f1 100644 > --- a/arch/x86/kernel/rtc.c > +++ b/arch/x86/kernel/rtc.c > @@ -14,6 +14,7 @@ > #include <asm/time.h> > #include <asm/intel-mid.h> > #include <asm/rtc.h> > +#include <asm/i8259.h> > > #ifdef CONFIG_X86_32 > /* > @@ -200,6 +201,10 @@ static __init int add_rtc_cmos(void) > } > #endif > > + /* RTC uses legacy IRQs. */ > + if (!nr_legacy_irqs()) > + return -ENODEV; > + > platform_device_register(&rtc_device); > dev_info(&rtc_device.dev, > "registered platform RTC device (no PNP device found)\n");
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