linux-kernel - Re: Qemu & KVM bug

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Date:	Wed, 13 Feb 2008 17:38:06 +0100
From:	"Zdenek Kabelac" <zdenek.kabelac@...il.com>
To:	"Marcelo Tosatti" <marcelo@...ck.org>
Cc:	"Jiri Kosina" <jkosina@...e.cz>, "Avi Kivity" <avi@...ranet.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Qemu & KVM bug

2008/2/13, Marcelo Tosatti <marcelo@...ck.org>:
> On Wed, Feb 13, 2008 at 04:24:53PM +0100, Jiri Kosina wrote:
> > On Wed, 13 Feb 2008, Zdenek Kabelac wrote:
> >
> > > I get this bug in my log whenever I start qemu-kvm - I do not use kqemu
> > > module - so it's with plain kernel modules. If more details are needed -
> > > just ask. (Cpu; C2D)
> > > BUG: sleeping function called from invalid context at kernel/rwsem.c:48
> > > in_atomic():1, irqs_disabled():0
> > > INFO: lockdep is turned off.
> > > Pid: 26600, comm: qemu-kvm Not tainted 2.6.25-rc1 #29
> >
> > This has been obviously caused by Marcelo's (added to CC) commit
> > 10589a4699b, which added down_write(mmap_sem) to alloc_apic_access_page(),
> > which is called with preempt disabled from vmx_create_vcpu().
>
> alloc_apic_access_page() called mutex_lock, so the warning would trigger
> before that change.
>
> I think it's fine to allocate the APIC page after put_cpu(), since no vcpu
> state is required.
>
> Avi?
>
>
> --- linux-2.6.orig/arch/x86/kvm/vmx.c
> +++ linux-2.6/arch/x86/kvm/vmx.c
> @@ -1601,9 +1601,6 @@ static int vmx_vcpu_setup(struct vcpu_vm

Hi

I've checked the patch myself - and looks like there is no BUG message
now - nice
thanks.

Zdenek
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