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RE: [Xen-devel] [PATCH] tweak memory error correction field in the SMBIO

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] tweak memory error correction field in the SMBIOS data
From: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Date: Thu, 26 Nov 2009 09:21:25 +0800
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Thread-topic: [Xen-devel] [PATCH] tweak memory error correction field in the SMBIOS data

Paolo Bonzini wrote:
> On 11/25/2009 04:00 PM, Jiang, Yunhong wrote:
>> So with your patch, even if host has no ECC support, you will still
>> tell guest that the memory has ECC?
> Yes, but I don't think it's of great importance.  I'm just pleasing a
> test with the simplest possible 1-line fix.  Do you know of anything
> that actually cares (i.e. not just "shows it to the user") about that
> particular DMI field, and does something different if it reads "ECC"?

One possible situation is, considering a host without ECC. When the host 
detected 1 bit memory error, it may raises #MCE. If we try to inject this #MCE 
to guest, guest will be confused, since DMI have report ECC support already.

Of course, I don't know if any host system will raise #MCE for such error, so 
it's more about a feeling that present guest with more capability than what 
host can provide is something tricky.

> For that matter, hvmloader is already saying that the host is
> running at
> some number of megahertz, which does not make sense for virtualization
> because the host may be loaded and slow down the guest.

Yes, but timer virtualization (especially the TSC virtualization) has taken a 
lot of effort on this  so that it make sense to guest, although sometime is 
relaxed with different timer mode.


> Paolo
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