Re: unhandled wrmsr

[Andre Przywara <andre.przywara@amd.com>]

Dave Young wrote:
> On Wed, Jun 2, 2010 at 8:45 PM, Andre Przywara <andre.przywara@amd.com> wrote:
>> Dave Young wrote:
>>> Hi,
>>>
>>> With today's git version (qemu-kvm), I got following message in kernel
>>> dmesg
>>>
>>> [168344.215605] kvm: 27289: cpu0 unhandled wrmsr: 0x198 data 0
>> Are you sure about that?
> 
> Sure
> 
> 0x198 is an Intel architectural perfmon MSR and it
>> is read-only. The Linux kernel source I grep'ed obeys this and does only
>> rdmsr.
>> You can work around this by changing the error to a warning with:
>> # modprobe kvm ignore_msrs=1
> 
> with this param, appear following warning:
> kvm: 28520: cpu0 ignored wrmsr: 0x198 data 0
As suspected. Did the boot succeed, then?
> 
>> I'd like to see more details about the guest Linux kernel, at least the
>> version you used to see why there is a wrmsr on this address. Best is you
>> provide the kernel (just the vmlinuz file) somewhere so that we can
>> reproduce this. Also the qemu-kvm command line would be interesting.
> 
> Actually I tried different guest image, recreate this problem is easy.
> 
> one of them is slackware 13.0 kernel version 2.6.29.6, you can download from:
> http://www.slackware.at/data/slackware64-13.0/kernels/huge.s/
Ah, nice to meet the other Slackware user ;-)

> kvm cmdline:
> qemu-system-x86_64 -net nic -net tap,ifname=tap0,script=no slack64.img
I tried:
$ x86_64-softmmu/qemu-system-x86_64 -kernel /boot/vmlinuz-huge-2.6.29.6 
-nographic -append "console=ttyS0,115200n8" -cpu 
core2duo,model=26,stepping=5,vendor=GenuineIntel
This booted fine.
Sadly I had no access to an Intel box this morning, so I had to use 
vendor override, but I guess this misses some features which an original 
Intel box has.
Can you post the /proc/cpuinfo output from the guest? It seems that some 
feature bits trigger the behavior in the guest. The host was an 
Xeon5520, right?

Regards,
Andre.

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12