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Re: [Xen-devel] [PATCH] [HVM] Fix virtual apic irq distribution

On 27 Jun 2006, at 12:39, Li, Xin B wrote:

But on our VM, we will have to synchronize TSC from time to time, so PIT
irq handler on different vcpu may see big TSC diff and complain about
the unreliable TSC, then maybe it will try to do TSC sync, which make
guest time keeping complex and unreliable.

How out-of-sync do TSCs of different VCPUs get?

I'd like to see a non-optimised TSC mode in which RDTSC always vmexits and we implement constant-rate always-sync'ed TSC in Xen. It'd be good to see if we could at least get that time mode working properly, and we'll need it anyway for save/restore/migration between machines with (even only slightly) different clock speeds or the guest will get very confused.

 -- Keir

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