RE: [Xen-devel] [RFC] Physical hot-add cpus and TSC

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

>-----Original Message-----
>From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
>Sent: Thursday, May 27, 2010 4:44 PM
>To: Jiang, Yunhong; Dan Magenheimer; Xen-Devel (xen-devel@xxxxxxxxxxxxxxxxxxx);
>Ian Pratt
>Subject: Re: [Xen-devel] [RFC] Physical hot-add cpus and TSC
>
>On 27/05/2010 07:15, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:
>
>>>>> get synced up before host software gets a look in. I don't think we can
>>>>> comment on whether or not there is an issue here without more
>>>>> information.
>>
>> Yes, this is a issue. The TSC will not be synched by firmware when hot-added,
>> at least I didn't find any spec on this, and my experiment shows the TSC 
>> value
>> is very small when new CPU is brought up. We need sync it in Xen side,
>>
>> Is it possible to sync the new-added CPU with the BSP when the CPU is added
>> (changed from non-present to present), as Keir suggested in previous mail? I
>> will have a look on the related code.
>
>I implemented this as xen-unstable:21468. This represents a strict
>improvement on what was in xen-unstable before that (no tsc sync at all,
>ever, because I deleted it about a week ago). Open to further improvements,
>if we can get consensus.

Thanks for the patch. I will get the system that support CPU hotplug tomorrow 
morning, I can try it then.

--jyh

>
> -- Keir
>


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