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Re: [Qemu-devel] [PATCH] resent: x86/cpuid: propagate further CPUID leaf

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH] resent: x86/cpuid: propagate further CPUID leafs when -cpu host
Date: Tue, 25 May 2010 10:27:58 +0300
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4

On 05/25/2010 01:10 AM, Anthony Liguori wrote:
On 05/21/2010 02:50 AM, Andre Przywara wrote:
-cpu host currently only propagates the CPU's family/model/stepping,
the brand name and the feature bits.
Add a whitelist of safe CPUID leafs to let the guest see the actual
CPU's cache details and other things.

Signed-off-by: Andre Przywara<address@hidden>

The problem I can see is that this greatly increases the chances of problems with live migration since we don't migrate the cpuid state.

-cpu host is already problematic for live migration.

Are you talking about the state maintained by the cpuid instruction? Yes, we need to migrate those bits.

What's the benefit of exposing this information to the guest?

Some algorithms adjust themselves based on the cache size. If you have several passes over a large data set, it's often better to run each set of passes on a subset of the dataset that fits in cache, then stitch the subsets together.

error compiling committee.c: too many arguments to function

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