linux-kernel - Re: [PATCH 3/4] x86, AMD: Fix crash as Xen Dom0 on AMD Trinity systems

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Date:	Thu, 7 Jun 2012 17:08:33 +0900
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Andre Przywara <andre.przywara@....com>
Cc:	Borislav Petkov <bp@...64.org>, "H. Peter Anvin" <hpa@...or.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jacob Shin <jacob.shin@....com>, jeremy@...p.org,
	xen-devel@...ts.xensource.com, LKML <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...e.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	stable@...r.kernel.org
Subject: Re: [PATCH 3/4] x86, AMD: Fix crash as Xen Dom0 on AMD Trinity
 systems

On Thu, Jun 07, 2012 at 09:49:01AM +0200, Andre Przywara wrote:
> On 06/07/2012 09:21 AM, Borislav Petkov wrote:
> >On Wed, Jun 06, 2012 at 03:00:14PM -0700, H. Peter Anvin wrote:
> >>On 06/01/2012 07:52 AM, Borislav Petkov wrote:
> >>>From: Andre Przywara<andre.przywara@....com>
> >>>
> >>>f7f286a910221 ("x86/amd: Re-enable CPU topology extensions in case BIOS
> >>>has disabled it") wrongfully added code which used the AMD-specific
> >>>{rd,wr}msr variants for no real reason.
> >>>
> >>>This caused boot panics on xen which wasn't initializing the
> >>>{rd,wr}msr_safe_regs pv_ops members properly.
> >>>
> >>>This, in turn, caused a heated discussion leading to us reviewing all
> >>>uses of the AMD-specific variants and removing them where unneeded
> >>>(almost everywhere except an obscure K8 BIOS fix, see 6b0f43ddfa358).
> >>>
> >>>Finally, this patch switches to the standard {rd,wr}msr*_safe* variants
> >>>which should've been used in the first place anyway and avoided unneeded
> >>>excitation with xen.
> >>>
> >>>Signed-off-by: Andre Przywara<andre.przywara@....com>
> >>>Cc: Andreas Herrmann<andreas.herrmann3@....com>
> >>>Cc: stable@...r.kernel.org # 3.4+
> >>>Link:<http://lkml.kernel.org/r/1338383402-3838-1-git-send-email-andre.przywara@amd.com>
> >>>[Boris: correct and expand commit message]
> >>>Signed-off-by: Borislav Petkov<borislav.petkov@....com>
> >>
> >>Why -stable?  I though we had agreed that we didn't have an active
> >>problem (unclean hack, yes, but not an active problem) in 3.4/3.5 as it
> >>currently sits?
> 
> This is probably a leftover from the original patch, before Konrad's
> patch got committed.
> 
> >Yes, AFAICT, we need at least one fix for 3.4 where the original patch
> >f7f286a910221 broke xen.
> >
> >So either this one or 1ab46fd319bc should be backported to stable, if
> >I'm not mistaken. If the second, I'll drop the stable tag from this one
> >and resend.
> >
> >Konrad, what do you want wrt xen paravirt nullptr breakage for
> >3.4-stable?
> 
> Greg just sent out the review mail for 1ab46fd319bc, so we can drop
> the stable tag from this one.
> 
> Regards,
> Andre.

What?  So I don't need to do anything?

Totally confused,

greg k-h
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