Re: [Xen-devel] [PATCH] TSC scaling for live migration between platforms with different TSC frequecies

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Stuffing the guest freq in a save-image pad field is not backward
compatible. Old images will not have that field filled in and you'll
probably end up doing something stupid like give them a zero-hertz TSC.
Please think about backward compatibility and use a separate save record.
Like Tim asked you to do already.

 -- Keir

On 22/06/2009 06:14, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> wrote:

> Hi, Keir
> This is the new version which has addressed the comments from the mailing
> list. Please review it again.  Thanks!
> Xiantao
> 
> Zhang, Xiantao wrote:
>> Hi, Keir
>> 
>>     This patchset targets for enabling TSC scaling in software for
>>     live migration between platforms with different TSC frequecies.
>> Once found the target host's frequency is different with source
>> host's, hypervisor will trap and emulate guest's all rdtsc
>> instructions with its expected frequency. If hardware's TSC frequency
>> is difffernt with guest's exepcted freq, guest may behave abnormally,
>> eg. incorrect wallclock, soft lockup, even hang in some cases.
>> Therefore, this patchset is necessary to avoid such issues.
>> 
>> PATCH 0001-- Save guest's preferred TSC in image for save/restore and
>> migration 
>> PATCH 0002-- Move multidiv64 as a library function.
>> PATCH 0003-- Scaling host TSC freqeuncy patch.
>> 
>> Signed-off-by Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
>> Xiantao
> 



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel