Messages in this thread Patch in this message | | | Date | Wed, 2 Dec 2015 14:55:34 +0000 | From | David Vrabel <> | 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 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 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"); -- 2.1.4
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