Re: WARNING: at arch/x86_64/kernel/smp.c:379 smp_call_function_single()

Avi Kivity
2007-08-19T10:55:13Z

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Avi Kivity wrote:
> Paolo Ornati wrote:
>> On Fri, 10 Aug 2007 14:04:33 +0200
>> "Michal Piotrowski" <michal.k.k.piotrowski@gmail.com> wrote:
>>
>>
>>>> [ 756.707601] Disabling non-boot CPUs ...
>>>> [ 756.712034] kvm: disabling virtualization on CPU1
>>>> [ 756.712037] WARNING: at arch/x86_64/kernel/smp.c:379
>>>> smp_call_function_single()
>>>> [ 756.712039]
>>>> [ 756.712039] Call Trace:
>>>> [ 756.712046] [<ffffffff8021d159>]
>>>> smp_call_function_single+0x119/0x120
>>>> [ 756.712050] [<ffffffff80542169>] thread_return+0x1bf/0x626
>>>> [ 756.712054] [<ffffffff80234b5b>] sys_sched_yield+0x2b/0x80
>>>> [ 756.712057] [<ffffffff8043684b>] kvm_cpu_hotplug+0x4b/0xa0
>>>> [ 756.712060] [<ffffffff80247c83>] notifier_call_chain+0x53/0x80
>>>> [ 756.712062] [<ffffffff80247d09>]
>>>> __raw_notifier_call_chain+0x9/0x10
>>>> [ 756.712065] [<ffffffff80247d21>] raw_notifier_call_chain+0x11/0x20
>>>> [ 756.712068] [<ffffffff8026184b>] take_cpu_down+0x1b/0x30
>>>> [ 756.712071] [<ffffffff802699d2>] do_stop+0xd2/0x150
>>>> [ 756.712073] [<ffffffff80269900>] do_stop+0x0/0x150
>>>> [ 756.712076] [<ffffffff8024f84d>] kthread+0x4d/0x80
>>>> [ 756.712079] [<ffffffff8020cb28>] child_rip+0xa/0x12
>>>> [ 756.712081] [<ffffffff8020c23c>] restore_args+0x0/0x30
>>>> [ 756.712084] [<ffffffff8024f800>] kthread+0x0/0x80
>>>> [ 756.712086] [<ffffffff8020cb1e>] child_rip+0x0/0x12
>>>> [ 756.712087]
>>>> [ 756.815693] CPU 1 is now offline
>>>> [ 756.815697] lockdep: not fixing up alternatives.
>>>> [ 756.819276] CPU1 is down
>>>>
>>>>
>>> Added to KR list, thanks for the report.
>>>
>>
>>
>> I've bisected it down to this commit:
>>
>> cec9ad279b66793bee0b5009b7ca311060061efd
>>
>> KVM: Use CPU_DYING for disabling virtualization
>> Only at the CPU_DYING stage can we be sure that no user
>> process will
>> be scheduled onto the cpu and oops when trying to use virtualization
>> extensions.
>>
>>
>
> Thanks. I'll have a go at it.
>
>

Sorry about the delay -- here is the fairly simple patch. A Tested-by:
would be appreciated.

--
error compiling committee.c: too many arguments to function

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>From a8c346b28695b938018f4bafd458f6d3e70c36e3 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@qumranet.com>
Date: Sun, 19 Aug 2007 13:51:00 +0300
Subject: [PATCH] KVM: Avoid calling smp_call_function_single() with interrupts disabled

When taking a cpu down, we need to hardware_disable() it. Unfortunately,
the CPU_DYING notifier is called with interrupts disabled, which means
we can't use smp_call_function_single(). Fortunately, the CPU_DYING notifier
is always called on the dying cpu, so we don't need to use the function at
all and can simply call hardware_disable() directly.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---
drivers/kvm/kvm_main.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 9685609..cd05579 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2974,6 +2974,10 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
switch (val) {
case CPU_DYING:
case CPU_DYING_FROZEN:
+ printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
+ cpu);
+ hardware_disable(NULL);
+ break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
--
1.5.2.4