linux-kernel - Re: [PATCH] Add MCE support to KVM

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Message-ID: <20090413082603.GS14687@one.firstfloor.org>
Date:	Mon, 13 Apr 2009 10:26:03 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Huang Ying <ying.huang@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add MCE support to KVM

On Sat, Apr 11, 2009 at 03:25:19PM +0300, Avi Kivity wrote:
> Andi Kleen wrote:
> >>Right, but we can allocate the maximum number, no?  it's a fairly small 
> >>amount of memory.
> >>    
> >
> >There are 255 banks worst case which need upto 4 (in theory 5) MSRs each
> >
> >  
> 
> That's 8KB, which would normally not be allocated.  But I think we can 
> live with it.
> 
> Do we actually need to support 255 banks? 

Probably not. Current CPUs all have a single digit number.

e.g. 64 would be plenty for now.

> Or can we support a smaller 
> number transparently?

Not transparently. In theory software can hardcode that for cpu model X bank Y 
is available and does Z. Software doesn't have too, Intel provides a bank 
independent way to report errors too, but we don't know if everyone uses it.
Linux doesn't rely on bank numbers on Intel at least.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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