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[Qemu-devel] Re: [PATCH] introduce kvm64 CPU

From: Andre Przywara
Subject: [Qemu-devel] Re: [PATCH] introduce kvm64 CPU
Date: Fri, 21 Aug 2009 23:53:41 +0200
User-agent: Thunderbird (X11/20081105)

Glauber Costa wrote:
On Fri, Aug 21, 2009 at 12:41 PM, Avi Kivity<address@hidden> wrote:
On 08/21/2009 12:34 AM, Andre Przywara wrote:
In addition to the TCG based qemu64 type let's introduce a kvm64 CPU type,
which is the least common denominator of all KVM-capable x86-CPUs
(based on Intel Pentium 4 Prescott). It can be used as a base type
for migration.

Typically users will want more specialized greatest common denomiator cpu
types; if a site has standardized on recent hardware they will want the
features of that hardware exposed.

I think this is best left to management software, which has more information
about the migration pool.
I believe what we want is an automatic tool that will connect to a
list of machines,and determine which qemu cpu type we should use.
> Doesn't sound like black magic...
I already have such a basic tool. It uses ssh (with pubkey) to connect to the target machine, then uses dd on /dev/cpu/0/cpuid to get the CPUID info. This requires cpuid.ko to be loaded and the permissions on the device file to be sufficient (the appropriate udev patch is already upstream). It then computes the least common denominator bits from several machines. Were you thinking of that approach or do you want to include this host CPUID functionality into QEMU (somehow embedded in the migration handler)?


Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
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