Re: [PATCH] KVM: Fix kvm_irqfd_init initialization

[Gleb Natapov <gleb@redhat.com>]

On Tue, May 07, 2013 at 06:11:33PM +0300, Michael S. Tsirkin wrote:
> On Tue, May 07, 2013 at 11:05:12PM +0800, Asias He wrote:
> > On Tue, May 07, 2013 at 05:59:38PM +0300, Michael S. Tsirkin wrote:
> > > On Tue, May 07, 2013 at 10:54:16PM +0800, Asias He wrote:
> > > > In commit a0f155e96 'KVM: Initialize irqfd from kvm_init()', when
> > > > kvm_init() is called the second time (e.g kvm-amd.ko and kvm-intel.ko),
> > > > kvm_arch_init() will fail with -EEXIST,
> > > 
> > > Wow. Is this intentional?
> > 
> > I think it is. You can not be amd and intel at the same time ;-)
> > 
> > kvm_arch_init
> > 
> >     if (kvm_x86_ops) {
> >             printk(KERN_ERR "kvm: already loaded the other module\n");
> >             r = -EEXIST;
> >             goto out;
> >     }       
> > 
> 
> Interesting. So we check it with
> 	if (kvm_x86_ops)
>  and later we do
>         kvm_x86_ops = ops;
> 
> 
> This looks racy - or is something serializing
> module loading?
> 
I think module loading is serialized.

--
			Gleb.