OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> writes:
> I noticed recently NMI on guest kernel is not working well. host/guest
> kernel is 2.6.39-rc4, and using vmx.
>
> And test code is something like the following:
>
> local_irq_disable();
> for (i = 0; i < 10; i++) {
> int cpu = get_cpu();
> printk("%s: nmi %u, lapic %u\n", __FUNCTION__,
> nmi_count(cpu), irq_stat[cpu].apic_timer_irqs);
> mdelay(1000);
> put_cpu();
> }
>
> the result is both of nmi and lapic are not increased. If I used
> -no-kvm-irqchip, it works fine (increase nmi only). So, it seems to be
> the bug of kvm driver side.
With some debug, the cause seems to be in pit_do_work(). With the
following patch, NMI watchdog seems to be working correctly (if irq
disabled for long time, NMI watchdog can detect it).
Is the following patch right?
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
[PATCH] kvm: Fix NMI on irq disabled state
On irq disabled state, there is no ->irq_ask from quest kernel. But
NMI shouldn't be affected by it.
This fixes inject NMI unconditionally.
Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/i8254.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff -puN arch/x86/kvm/i8254.c~kvm-nmi-fix arch/x86/kvm/i8254.c
--- linux-2.6/arch/x86/kvm/i8254.c~kvm-nmi-fix 2011-04-24 07:42:23.000000000 +0900
+++ linux-2.6-hirofumi/arch/x86/kvm/i8254.c 2011-04-24 07:42:23.000000000 +0900
@@ -305,20 +305,20 @@ static void pit_do_work(struct work_stru
if (inject) {
kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1);
kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0);
-
- /*
- * Provides NMI watchdog support via Virtual Wire mode.
- * The route is: PIT -> PIC -> LVT0 in NMI mode.
- *
- * Note: Our Virtual Wire implementation is simplified, only
- * propagating PIT interrupts to all VCPUs when they have set
- * LVT0 to NMI delivery. Other PIC interrupts are just sent to
- * VCPU0, and only if its LVT0 is in EXTINT mode.
- */
- if (kvm->arch.vapics_in_nmi_mode > 0)
- kvm_for_each_vcpu(i, vcpu, kvm)
- kvm_apic_nmi_wd_deliver(vcpu);
}
+
+ /*
+ * Provides NMI watchdog support via Virtual Wire mode.
+ * The route is: PIT -> PIC -> LVT0 in NMI mode.
+ *
+ * Note: Our Virtual Wire implementation is simplified, only
+ * propagating PIT interrupts to all VCPUs when they have set
+ * LVT0 to NMI delivery. Other PIC interrupts are just sent to
+ * VCPU0, and only if its LVT0 is in EXTINT mode.
+ */
+ if (kvm->arch.vapics_in_nmi_mode > 0)
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ kvm_apic_nmi_wd_deliver(vcpu);
}
static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
_
--
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