Re: [RFC PATCH v2 2/2] add support for Hyper-V invariant TSC

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, May 23, 2013 at 10:53:38AM -0300, Marcelo Tosatti wrote:
> On Thu, May 23, 2013 at 12:12:29PM +0300, Gleb Natapov wrote:
> > > To address migration scenarios to physical platforms that do not support
> > > iTSC, the TscSequence field is used. In the event that a guest partition
> > > is  migrated from an iTSC capable host to a non-iTSC capable host, the
> > > hypervisor sets TscSequence to the special value of 0xFFFFFFFF, which
> > > directs the guest operating system to fall back to a different clock
> > > source (for example, the virtual PM timer)."
> > > 
> > > Why it would not/does not work after migration?
> > > 
> > Please read the whole discussion, we talked about it already. We
> > definitely do not want to fall back to PM timer either, we want to use
> > reference counter instead.
> 
> Case 1) On migration of TSC page enabled Windows guest, from invariant TSC host,
> to non-invariant TSC host, Windows guests fallback to PMTimer
> and not to reference timer via MSR. 
> 
> This is suboptimal because pmtimer emulation is excessively slow.
> 
> Is there a better option?
> 
If setting TscSequence to zero makes Windows fall back to the MSR this is a
better option.

> Case 2)
> Reference timer (via MSR) support is interesting for the case of non invariant TSC
> host.

--
			Gleb.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux