Re: hyper-v support in KVM

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On Fri, 2014-02-14 at 02:35 +0000, Liu, RongrongX wrote:
> > -----Original Message-----
> > From: Vadim Rozenfeld [mailto:vrozenfe@redhat.com]
> > Sent: Wednesday, February 12, 2014 3:42 PM
> > To: Zhang, Yang Z
> > Cc: kvm@vger.kernel.org; Liu, RongrongX
> > Subject: Re: hyper-v support in KVM
> > 
> > On Wed, 2014-02-12 at 01:33 +0000, Zhang, Yang Z wrote:
> > > Vadim Rozenfeld wrote on 2014-02-10:
> > > > On Mon, 2014-02-10 at 08:21 +0000, Zhang, Yang Z wrote:
> > > >> Hi Vadim,
> > > >>
> > > >> Do you know the latest status of Hyper-v Enlightenments supporting in
> > KVM?
> > > > Like how many Hyper-v interfaces are supported in KVM?
> > > >
> > > > Hi Yang,
> > > >
> > > > There is no many at the moment. KVM currently supports the following
> > > > Hyper-V features:
> > > >
> > > > Guest Spinlocks
> > > > http://msdn.microsoft.com/en-us/library/windows/hardware/ff539081%
> > > > 28v=vs.85%29.aspx
> > > >
> > > > Local APIC MSR Accesses
> > > > http://msdn.microsoft.com/en-us/library/windows/hardware/ff542396%
> > > > 28v=vs.85%29.aspx
> > > >
> > > > Reference Time Counter
> > > > http://msdn.microsoft.com/en-us/library/windows/hardware/ff542637%
> > > > 28v=vs.85%29.aspx
> > > >
> > > > We are going to add: Reference TSC Page
> > > > http://msdn.microsoft.com/en-us/library/windows/hardware/ff542643%
> > > > 28v=vs.85%29.aspx
> > > >
> > > > Lazy EOI support, maybe more.
> > > >
> > >
> > > Thanks for your update. More questions:
> > > I want to measure the performance improvement with hyper-v features
> > enabled. So I want to know:
> > > Are those features enabled by default in KVM?
> > In KVM - yes, but you also need to specify them in QEMU command line.
> > They can be enabled by -cpu features hv_vapic, hv_spinlocks, hv_time, and
> > hv_relaxed
> Hi Vadim,
> in QEMU command line, how to enable these feature?
> I try it with
> 1. [root@vt-snb9 ]#qemu-system-x86_64 -enable-kvm -m 2048 -smp 2 -net none win8.1.img -cpu feature hv_vapic,+hv_spinlocks,+hv_time,+hv_relaxed
>  qemu-system-x86_64: -cpu feature: drive with bus=0, unit=0 (index=0) exists
> 2. [root@vt-snb9]# qemu-system-x86_64 -enable-kvm -m 2048 -smp 2 -net none win8.1.img -cpu qemu64,+hv_vapic,+hv_spinlocks,+hv_time,+hv_relaxed

something like this:
-cpu qemu64,
+x2apic,family=0xf,hv_vapic,hv_spinlocks=0xfff,hv_relaxed,hv_time

(for hv_vapic we also need x2apic to be enabled)

Best regards,
Vadim.

> CPU feature hv_vapic not found
> CPU feature hv_spinlocks not found
> CPU feature hv_time not found
> CPU feature hv_relaxed not found
> CPU feature hv_vapic not found
> CPU feature hv_spinlocks not found
> CPU feature hv_time not found
> CPU feature hv_relaxed not found
> VNC server running on `::1:5900'
> 
> 
> > > How to turn off/on it manually?
> > Yes. From the QEMU command line.
> > 
> > > And how can I know whether guest is using it really?
> > There are two options - printk from the KVM side or WinDbg from the guest
> > side. But in case of hv_time you can check the value returned by
> > QueryPerformanceFrequency
> > http://msdn.microsoft.com/en-us/library/windows/desktop/ms644905%
> > 28v=vs.85%29.aspx
> > it should be 10MHz
> > 
> > >  Also, Do you have any performance data?
> > http://www.linux-kvm.org/wiki/images/0/0a/2012-forum-kvm_hyperv.pdf
> > pp 16, 18
> > I compared DPC and ISR times with xperf for two cases - with and without
> > enlightenment.
> > I also have seen reports mentioned around 5-10 percent CPU usage drop on the
> > host side, when loading guest with some disk-stress tests.
> > 
> > >
> > > > Kind regards.
> > > > Vadim.
> > > >
> > > >>
> > > >> best regards
> > > >> yang
> > > >>
> > > >> --
> > > >> To unsubscribe from this list: send the line "unsubscribe kvm" in
> > > >> the body of a message to majordomo@vger.kernel.org More majordomo
> > > >> info at  http://vger.kernel.org/majordomo-info.html
> > > >
> > > >
> > >
> > >
> > > Best regards,
> > > Yang
> > >
> > >
> > 
>