On 9/16/15 6:00 AM, David Matlack wrote:
On Tue, Sep 15, 2015 at 12:04 AM, Oliver Yang <yang_oliver@xxxxxxxxxxx> wrote:
Hi Guys,
I found below patch for KVM TSC trapping / migration support,
https://lkml.org/lkml/2011/1/6/90
It seemed the patch were not merged in Linux mainline.
So I have 3 questions here,
1. Can KVM support TSC trapping today? If not, what is the plan?
Not without a patch. Did you want to trap RDTSC? RDTSC works without
trapping thanks to hardware support.
2. What is the solution if my SMP Linux guest OS doesn't have reliable
TSC?
If you are seeing an unreliable TSC in your guest, maybe your host
hardware does not support a synchronized TSC across CPUs. I can't
recall how to check for this. There might be a flag in your host's
/proc/cpuinfo.
constant_tsc
Because the no TSC trapping support, will kvmclock driver handle all
TSC sync issues?
3. What if my Linux guest doesn't have kvmclock driver?
The guest will use a different clock source (e.g. acpi-pm). Note the
RDTSC[P] instruction will still work just fine.
Does that mean I shouldn't run TSC sensitive application in my guest
OS?
BTW, my application is written with lots of rdtsc instructions, and
which performs well in VMware guest.
Does it not work well in KVM?
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