Re: Xen 4.2 TODO / Release Plan

["Liu, Jinsong" <jinsong.liu@intel.com>]

Jan Beulich wrote:
>>>> On 03.08.12 at 12:28, Keir Fraser <keir.xen@gmail.com> wrote:
>> On 03/08/2012 11:09, "Ian Campbell" <Ian.Campbell@citrix.com> wrote:
>> 
>>> On Mon, 2012-07-30 at 09:30 +0100, Ian Campbell wrote:
>>>>     * vMCE save/restore changes, to simplify migration 4.2->4.3
>>>>      with new vMCE in 4.3. (Jinsong Liu, Jan Beulich)
>>> 
>>> Where are we with this?
>>> 
>>> Is it still a viable candidate for 4.2, now that we have reached rc1
>>> (almost 2)?
>> 
>> Didn't we already take the trivial patch that will ease the
>> transition to 
>> 4.3?
> 
> We took one necessary patch, but I think at least the second
> one of the recently posted series would also be needed. And
> the really important patch for migration forward compatibility
> was patch 5 in that series, yet I wouldn't want to take patches
> 3 and 4 for 4.2.
> 
> In any case, the series is in need of resubmission anyway.
> Perhaps (if that's possible, I didn't check in too much detail)
> reordering patch 5 could be done at once.
> 

Patch 2 has been updated according to Jan's comments.

As for patch 5, it cannot be reordered w/o patch 3 checked in (patch 5 is for save/restore MCi_CTL2, a newly added MSR at patch 3). In fact we could remove patch 5 totally, and don't add MCi_CTL2 (this MSR is nothing to do with vmce logic itself, the only reason why we add it in new vmce is to get perfromance benefit (but very trivial), so it's OK not to add it and remove patch 5). Another benefit of not add MCi_CTL2 is, to avoid difference between Intel and AMD code. Hence I think it's an acceptable approach to keep current vmce (not implement MCi_CTL2). Your opinion?

Thanks,
Jinsong