linux-kernel - RE: [xen vMCE RFC V0.2] xen vMCE design

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Message-ID: <DE8DF0795D48FD4CA783C40EC8292335264914@SHSMSX101.ccr.corp.intel.com>
Date:	Thu, 28 Jun 2012 13:38:36 +0000
From:	"Liu, Jinsong" <jinsong.liu@...el.com>
To:	Jan Beulich <JBeulich@...e.com>, "Auld, Will" <will.auld@...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>,
	"Luck, Tony" <tony.luck@...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: [xen vMCE RFC V0.2] xen vMCE design

Jan Beulich wrote:
>>>> On 28.06.12 at 11:40, "Liu, Jinsong" <jinsong.liu@...el.com> wrote:
>> So I would like to push new vMCE as quickly as possible. What's the
>> timeline of vMCE developing that xen 4.2 could accept?
> 
> Weeks ago, really. See
> http://lists.xen.org/archives/html/xen-devel/2012-06/msg01619.html
> and follow-ups - we'd really only consider getting the save/restore 
> interface into forward compatible shape as acceptable.
> 
>> I wonder if we could make major
>> components of vMCE done before xen 4.2 timeline, and leave the
>> surrounding features and the corner cases done later?
> 
> Unfortunately it's likely going to be even less. However, if split
> that way, chances are things could go into e.g. 4.2.1.
> 
> Jan

So let's look at current vMCE status first:
1). functionally it work abnormally for guest (but tolerated by some guest like linux/solaris);
2). before xen 4.1 it blocks migration when migrate from big bank to small bank platform;

We may try some middle steps, minimal adjusting for xen 4.2 release (to avoid futher compatible issue at xen 4.2.1, 4.3, ...):
1). we don't handle vMCE function bugs, only make sure migration works OK;
2). update vMCE interface to a middle clean status:
    * remove MCG_CTL (otherwise we have to add this useless MSR at new vMCE);
    * stick all 1's to MCi_CTL (avoid semantic difference);
    * for MCG_CAP, clear MCG_CTL_P, limit to 2 banks (otherwise dirty code have to be added at new vMCE);

Thoughts?

Thanks,
Jinsong--
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