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Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation

On 10/14/2009 05:00 AM, Jeremy Fitzhardinge wrote:

So it's broken or disabled when that assumption is wrong?  We could
easily fix that now.  Might even reuse the pvclock structures.
Well, the kernel internally makes more or less the same assumption; the
vsyscall clocksource is the same as the kernel's internal one.  I think
idea is that it just drops back to something like hpet if the tsc
doesn't have very simple SMP characteristics.

If the kernel could characterize the per-cpu properties of the tsc more
accurately, then it could use the pvclock mechanism on native.

It does - that's how kvm implements pvclock on the host side. See kvmclock_cpufreq_notifier() in arch/x86/kvm/x86.c.

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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