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Re: [Xen-devel] Re: [Xen-staging] [xen-unstable] Added some more fields

To: Alex Williamson <alex.williamson@xxxxxx>, <ewan@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-staging] [xen-unstable] Added some more fields to host_cpu.
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 02 Mar 2007 20:46:05 +0000
Cc: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Hollis Blanchard <hollisb@xxxxxxxxxx>
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Thread-topic: [Xen-devel] Re: [Xen-staging] [xen-unstable] Added some more fields to host_cpu.
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On 2/3/07 20:39, "Alex Williamson" <alex.williamson@xxxxxx> wrote:

>   On ia64, dom0 doesn't automatically get vcpus for each physical cpu,
> so the first problem is that we're not going to have a /proc/cpuinfo
> entry for every cpu in self.cpus.keys.  I think it's likely x86 could
> run into this problem too if a cpu was hotplugged or booted with the
> dom0_max_vcpus options.

We have indeed hit this problem and I put a patch in this afternoon to
duplicate cpu0's info for any non-existent cpu. Given that the dom0 cpus
could be migrating around on arbitrary physical cpus (even across the
multiple CPUID invocations that the kernel will have made to build the
information for a single 'cpu' in /proc!) this is fine -- x86 multiprocessor
systems are supposed to be symmetric (homogeneous CPUs down to the same
stepping in some cases) anyway.

 -- Keir

>    The second problem is that /proc/cpuinfo fields are very architecture
> specific.  I'd suggest importing arch and having separate cases for x86,
> ia64, and powerpc.  For ia64, think the most appropriate mapping would
> be:

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