From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@qumranet.com>
Subject: Re: [PATCH]: Fake MSR_K7 performance counters
Date: Fri, 02 May 2008 13:00:10 +0300
Message-ID: <481AE62A.3050306@qumranet.com>
References: <4815FF35.70809@redhat.com> <4819D261.5050305@redhat.com>
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Cc: kvm-devel <kvm-devel@lists.sourceforge.net>
To: Chris Lalancette <clalance@redhat.com>
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Chris Lalancette wrote:
> Chris Lalancette wrote:
>   
>> Attached is a patch that fixes a guest crash when booting older Linux kernels.
>> The problem stems from the fact that we are currently emulating
>> MSR_K7_EVNTSEL[0-3], but not emulating MSR_K7_PERFCTR[0-3].  Because of this,
>> setup_k7_watchdog() in the Linux kernel receives a GPF when it attempts to write
>> into MSR_K7_PERFCTR, which causes an OOPs.
>>
>> The patch fixes it by just "fake" emulating the appropriate MSRs, throwing away
>> the data in the process.  This causes the NMI watchdog to not actually work, but
>> it's not such a big deal in a virtualized environment.
>>
>> Tested by myself on a RHEL-4 guest, and Joerg Roedel on a Windows XP 64-bit guest.
>>     
>
> Avi,
>      Do you mind applying this patch for me (unless you see something wrong with
> it, of course)?
>
>   

Sorry, was behind on my email. Please add a ratelimited printk() if 
nonzero data is written, so that we know that the guest is using 
partially virtualized features.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.


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