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[Xen-devel] Re: Memory hot-add and c/s 20892: bad interaction?

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Yunhong Jiang" <yunhong.jiang@xxxxxxxxx>
Subject: [Xen-devel] Re: Memory hot-add and c/s 20892: bad interaction?
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Mon, 08 Feb 2010 11:09:19 +0000
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>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 08.02.10 11:32 >>>
>I was just thinking about xen-unstable:20892, which exposes real current
>max_mfn to guests, so that they can more accurately clamp their m2p address
>translations.
>
>I was wondering whether this changeset is actually a bad idea in light of
>memory hot-add, as now implemented by Yunhong? I would imagine this can mean
>that max_mfn is now dynamic, and can increase in value after boot. So would
>20892 thus leave all existing guests (e.g., dom0!) broken after a hot-add
>which adds new highest RAM addresses?

You probably overlooked the

+        if ( !mem_hotplug )

in that patch? I was intending to return some sort of boundary for the
hot-add case too, but that needs propagation from the SRAT parsing
code, and I didn't think that would be urgent (i.e. for 4.0).

Jan


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