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<p>I think I've read about this on this mailing list, because when
playing Crysis 3, my VM kept crashing (more precise: the game
didn't even start), until I set 'options kvm ignore_msrs=1' in
modprobe.d .conf file.<br>
When switching to Win8, will the performance be better?</p>
<p><br>
</p>
<p>Thanks,</p>
<p>Marius<br>
</p>
<br>
<div class="moz-cite-prefix">Am 06.01.2017 um 14:52 schrieb Quentin
Deldycke:<br>
</div>
<blockquote
cite="mid:CAHYLta6vF9TqCC6waR+xd0be_1f=qO8snOBUzQ6nvqLVFSADXQ@mail.gmail.com"
type="cite">
<div dir="ltr">For adding a bit on this subjects, some games
(blizzard games, tomb raider at it's launch) use a lot of msrs
during run.
<div>It seems this is made for their anti-cheat / hack systems.</div>
<div><br>
</div>
<div>Heroes of the storm, SC2 are spamming these msrs. This
reduce performance quite hardly.</div>
<div><br>
</div>
<div>Funny thing: This "bug" does not apply to win8 / win7 :)</div>
<div><br>
</div>
<div>For reference we spoke about such in this thread a long
time ago:</div>
<div><a moz-do-not-send="true"
href="https://www.redhat.com/archives/vfio-users/2016-May/msg00134.html">https://www.redhat.com/archives/vfio-users/2016-May/msg00134.html</a><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>The kernel spam of such error at Heroes of the storm login
screen:</div>
<div>
<div>[136995.284205] kvm [6799]: vcpu2, guest rIP:
0xfffff8016e757733 kvm_set_msr_common: MSR_IA32_DEBUGCTLMSR
0x1, nop</div>
<div>[136995.284217] kvm [6799]: vcpu2, guest rIP:
0xfffff8016e757733 kvm_set_msr_common: MSR_IA32_DEBUGCTLMSR
0x1, nop</div>
<div>[137000.285330] kvm_get_msr_common: 302015 callbacks
suppressed</div>
<div>[137000.285337] kvm [6799]: vcpu5, guest rIP:
0xfffff8016e75779c ignored rdmsr: 0x1c9</div>
<div>[137000.285342] kvm [6799]: vcpu5, guest rIP:
0xfffff8016e7577aa ignored rdmsr: 0x680</div>
<div>[137000.285344] kvm [6799]: vcpu5, guest rIP:
0xfffff8016e7577c1 ignored rdmsr: 0x6c0</div>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br clear="all">
<div>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">--
<div>Deldycke Quentin<br>
</div>
<div>
<div><br>
</div>
</div>
</div>
</div>
</div>
<br>
<div class="gmail_quote">On 6 January 2017 at 14:07, Thomas
Lindroth <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:thomas.lindroth@gmail.com" target="_blank">thomas.lindroth@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"><span
class="">On 01/06/2017 01:00 PM, Marius Steffen wrote:<br>
</span><span class="">> Is there anything I can do to a)
find the cause of this bad performance<br>
> b) make my VM perform better?<br>
<br>
</span>One thing you can try is to run the game with poor
performance and at the<br>
same time run "perf kvm --host stat live" on the host. This
will show how<br>
many VM-EXIT kvm performs. VM-EXIT means the guest has done
something the<br>
hardware virtualisation can't handle, like accessing MSR or
virtual IO.<br>
<br>
Some workloads will perform badly because they cause a lot
of VM-EXIT.<br>
Perf will tell you why a VM-EXIT was performed. The more
common causes are<br>
IO_INSTRUCTION and EPT_MISCONFIG. IO_INSTRUCTION means the
guest tried to<br>
access an x86 ioport and EPT_MISCONFIG seems to be an odd
name for access<br>
to memory mapped io. Sometimes a lot of time is spent in HLT
but that's<br>
normal. It only means the guest OS has nothing to do and
goes idle.<br>
<br>
By running "perf kvm --host stat live --event=ioport" you
can check which<br>
ioport is accessed and "perf kvm --host stat live
--event=mmio" shows<br>
which address was accessed for memory mapped io.<br>
<br>
If you see that an mmio address is accessed a lot and want
to find out what<br>
it is you can run "virsh qemu-monitor-command
<nameofvm> --hmp 'info mtree'"<br>
to get a list of the memory layout of the VM. Unfortunately
I don't know<br>
of any way to get a similar list of ioports.<br>
<br>
As an example on my system some games like Rise of the Tomb
Raider and<br>
Assassin's Creed Unity will access ioport 0xb008 more than
200,000 times/sec<br>
and those games will have poor performance compared to
native. Qemu<br>
hardcode the acpi timer to ioport 0xb008 and those games
excessively read<br>
the hardware timer. I haven't figured out any way to work
around the problem<br>
but I run games with vsync on and even with the decreased
performance I get<br>
60fps in those titles.<br>
<div class="HOEnZb">
<div class="h5"><br>
______________________________<wbr>_________________<br>
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</div>
</blockquote>
</div>
<br>
</div>
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