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| Started by | David Vrabel <david.vrabel@citrix.com> |
|---|---|
| First post | 2015-12-02 16:00 +0100 |
| Last post | 2015-12-02 18:40 +0100 |
| Articles | 2 — 2 participants |
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Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. David Vrabel <david.vrabel@citrix.com> - 2015-12-02 16:00 +0100
Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. Sander Eikelenboom <linux@eikelenboom.it> - 2015-12-02 18:40 +0100
| From | David Vrabel <david.vrabel@citrix.com> |
|---|---|
| Date | 2015-12-02 16:00 +0100 |
| Subject | Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. |
| Message-ID | <qBh2W-8un-23@gated-at.bofh.it> |
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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| From | Sander Eikelenboom <linux@eikelenboom.it> |
|---|---|
| Date | 2015-12-02 18:40 +0100 |
| Subject | Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. |
| Message-ID | <qBjxO-1Sz-53@gated-at.bofh.it> |
| In reply to | #1281875 |
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"); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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