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Re: [Qemu-devel] [PATCH 2/3] push CPUID level to 4 to allow Intel multic

From: Andre Przywara
Subject: Re: [Qemu-devel] [PATCH 2/3] push CPUID level to 4 to allow Intel multicore decoding
Date: Tue, 25 Aug 2009 14:21:52 +0200
User-agent: Thunderbird (X11/20090329)

 Avi Kivity wrote:
> Andre Przywara wrote:
The only problem I can think of is that the advertised cache topology is somehow bogus and could confuse OSes.

So long as it's smaller than contemporary caches we should be fine.
Oh, I see now that Alex' Core2Duo (on which QEMU's leaf 4 values are based on) has 4 MB of L2-Cache. Although that is not gigantic for Intel CPUs, it's certainly too high for many host CPUs. I will lower this value to say 1MB or 512K to better match the majority of host. I will send a patch together with some more CPUID reworks I am working on.

btw, does -cpu host use the host cpu cache information?
Good point. It does not, it only deals with leaves 0, 1, 8000_0000 and 8000_0001. I have created a white list of further CPUID leaves which are safe to propagate to the guest and will also send this in a while.

Thanks for these hints,

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