linux-kernel - RE: [vMCE design RFC] Xen vMCE design

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Date:	Fri, 22 Jun 2012 15:29:41 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Jan Beulich <JBeulich@...e.com>,
	"Liu, Jinsong" <jinsong.liu@...el.com>
CC:	"Raj, Ashok" <ashok.raj@...el.com>,
	"Dugger, Donald D" <donald.d.dugger@...el.com>,
	"Shan, Haitao" <haitao.shan@...el.com>,
	"Nakajima, Jun" <jun.nakajima@...el.com>,
	"Li, Susie" <susie.li@...el.com>,
	"Auld, Will" <will.auld@...el.com>,
	"Zhang, Xiantao" <xiantao.zhang@...el.com>,
	"Jiang, Yunhong" <yunhong.jiang@...el.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Keir Fraser <keir@....org>
Subject: RE: [vMCE design RFC] Xen vMCE design

> 1). still use 1 bank and simply ignore this issue. I mean, even if guest 
> runs at bank0 quirks platform, when hypervisor inject vMCE# to guest, guest 
> skip bank0, then guest MCE logic would think it detect a spurious mce, then 
> kill itself. Considering bank0 quirks is only for old cpus, this is 
> acceptable;
> 2). use 32 banks
> 
> In fact, a third option is, use 1 bank, but hypervisor kill guest when it 
> detect bank0 quirks. This would be same effect as option 1, so I prefer let 
> guest kill itself.

Don't you control what CPUID is shown to the guest? Under what circumstances
would you tell the guest that it is running on an AMD-K7 or an Intel family
6 with model < 0x1A?   Surely for migration reasons you need to present the
same virtualized family/model all the time ... so just don't use ones that
cause problems.

If that isn't an option - then say there are 2 banks and have Xen ignore bank
0 (make MC0_STATUS always appear to contain 0) and put all the errors into
bank1.  If you tell the guest there are 32 banks it will read all of them.
Which means a lot of pointless exits to the hypervisor.

-Tony
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