Re: [Xen-devel] Re: [PATCH] Fix cpu hotplug bug of mtrr update i

To:	"Liu, Jinsong" <jinsong.liu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] Re: [PATCH] Fix cpu hotplug bug of mtrr update inconsistency
From:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date:	Tue, 1 Jun 2010 10:41:00 +0100
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On 01/06/2010 10:18, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> I suggest we leave the call where it is, and fix set_mtrr() to not race CPUs
> coming online. It is called elsewhere other than mtrr_ap_init() after all.
> Also if you call mtrr_ap_init() before being in cpu_online_map, you then
> race further MTRR changes:
>  - CPU X calls mtrr_ap_init()
>  - CPU Y calls set_mtrr() to actually change an MTRR.
>  - CPU X adds itself to cpu_online_map
>  - Aiee, CPU X is missing Y's update
> 
> I'll make a patch.

xen-unstable:21499.

 -- Keir



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Re: [Xen-devel] Re: [PATCH] Fix cpu hotplug bug of mtrr update inconsist