From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH for stable] x86/spinlocks/paravirt: Fix memory corruption
	on unlock
Date: Wed, 25 Feb 2015 11:08:06 +0100
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To: Greg KH <gregkh@linuxfoundation.org>
Cc: jeremy@goop.org, Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>, kvm@vger.kernel.org, peterz@infradead.org, virtualization@lists.linux-foundation.org, paul.gortmaker@windriver.com, hpa@zytor.com, ak@linux.intel.com, a.ryabinin@samsung.com, x86@kernel.org, borntraeger@de.ibm.com, mingo@redhat.com, xen-devel@lists.xenproject.org, paulmck@linux.vnet.ibm.com, riel@redhat.com, konrad.wilk@oracle.com, dave@stgolabs.net, sasha.levin@oracle.com, davej@redhat.com, tglx@linutronix.de, waiman.long@hp.com, oleg@redhat.com, stable@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, akpm@linux-foundation.org, torvalds@linux-foundation.org
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* Greg KH <gregkh@linuxfoundation.org> wrote:

> > >It's:
> > >
> > >  d6abfdb20223 x86/spinlocks/paravirt: Fix memory corruption on unlock
> > 
> > Yes, This is the original patch. Please note I have taken out the
> > READ_ONCE changes from the original patch to avoid build warnings
> > mentioned below.
> > (Those READ_ONCE changes were cosmetic and was not present in the
> > previous versions)
> > 
> > >
> > >You'll also need this fix from Linus to avoid (harmless)
> > >build warnings:
> > >
> > >  dd36929720f4 kernel: make READ_ONCE() valid on const arguments
> > 
> > So this may not be absolutely necessary with the current patch.
> 
> I'd prefer to be as close as possible to the upstream 
> patch.  So if applying both of these patches will work, 
> I'd much rather do that. Changing patches when 
> backporting them to stable for no good reason than to 
> clean things up, just confuses everyone involved.
> 
> Let's keep our messy history :)

By all means!

You'll first need to cherry-pick these commits:

 927609d622a3 kernel: tighten rules for ACCESS ONCE
 c5b19946eb76 kernel: Fix sparse warning for ACCESS_ONCE
 dd36929720f4 kernel: make READ_ONCE() valid on const arguments

That's the minimum set you will need for backporting, due 
to overlapping changes to the ACCESS_ONCE() definition.

and then apply this commit:

 d6abfdb20223 x86/spinlocks/paravirt: Fix memory corruption on unlock

I've double checked that these commits will cherry-pick 
fine on top of v3.19, in that order, and that an x86-64 
defconfig+kvmconfig+PARAVIRT_SPINLOCK=y kernel builds fine 
without warnings.

I've not boot tested the changes, so if anything breaks 
it's all your fault - while if it works just fine then
I'll be glad to take credit for that.

Thanks,

	Ingo