linux-kernel - Re: [PATCH 09/15] x86: Emergency virtualization disable function

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Message-ID: <20081106153405.GS5247@blackpad>
Date:	Thu, 6 Nov 2008 13:34:05 -0200
From:	Eduardo Habkost <ehabkost@...hat.com>
To:	Pavel Machek <pavel@...e.cz>
Cc:	Avi Kivity <avi@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Simon Horman <horms@...ge.net.au>,
	Andrew Morton <akpm@...l.org>, Vivek Goyal <vgoyal@...hat.com>,
	Haren Myneni <hbabu@...ibm.com>,
	Andrey Borzenkov <arvidjaar@...l.ru>, mingo@...hat.com,
	"Rafael J. Wysocki" <rjw@...k.pl>, kexec@...ts.infradead.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/15] x86: Emergency virtualization disable function

On Wed, Nov 05, 2008 at 11:27:32PM +0100, Pavel Machek wrote:
> On Wed 2008-11-05 17:56:52, Eduardo Habkost wrote:
> > This patch adds an interface to set a function that can be used to
> > disable virtualization extensions on the CPU on emergency cases, such
> > as on kdump or emergency reboot.
> > 
> > The function will be set by code that enables virtualization extensions
> > on the CPUs (i.e. KVM), and should do the very least to disable virt
> > extensions on the CPU where it is being called.
> > 
> > The functions that set the function pointer uses RCU synchronization,
> > just in case the crash NMI is triggered while KVM is unloading.
> > 
> > We can't just use the same notifiers used at reboot time (that are used
> > by non-crash-dump kexec), because at crash time some CPUs may have IRQs
> > disabled, so we can't use IPIs. The crash shutdown code use NMIs to tell
> > the other CPUs to be halted, so the notifier call will be hooked into
> > the CPU halting code that is on the crash shutdown NMI handler.
> > 
> > [v2: drop 'unsigned int cpu' arg from function]
> > [v3: make emergency_virt_disable() non-static]
> > [v4: add a config option for it: CPU_VIRT_EXTENSIONS]
> > [v5: add has_virt_extensions() function]
> > [v6: don't define the registering functions if CPU_VIRT_EXTENSIONS is
> >  not enabled]
> > [v7: use EXPORT_SYMBOL_GPL]
> > 
> 
> > --- /dev/null
> > +++ b/arch/x86/kernel/virtext.c
> > @@ -0,0 +1,89 @@
> > +/* Core CPU virtualization extensions handling
> > + *
> > + * This should carry the code for handling CPU virtualization extensions
> > + * that needs to live in the kernel core.
> > + *
> > + * Author: Eduardo Habkost <ehabkost@...hat.com>
> > + *
> > + * Copyright (C) 2008, Red Hat Inc.
> > + */
> 
> GPL?

Yes, of course.

As IANAL, I used a similar .c file as reference for the author/copyright
info header, and used arch/x86/kernel/crash.c, that doesn't refer to
the GPL also. I think I chose a bad example as reference.

arch/x86/kernel/crash.c even has "All rights reserved". Ouch.

-- 
Eduardo
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