From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: What's kvmclock's custom sched_clock for?
Date: Thu, 7 Jan 2016 08:56:47 -0200
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Cc: Radim Krcmar <rkrcmar@redhat.com>, kvm list <kvm@vger.kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
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On Wed, Jan 06, 2016 at 11:18:51PM -0800, Andy Lutomirski wrote:
> AFAICT KVM reliably passes a monotonic TSC through to guests, 

It does not.

> even if the host suspends. That's all that sched_clock needs, I think.
>
> So why does kvmclock have a custom sched_clock?

Migration between hosts with different TSC frequencies.

> On a related note, KVM doesn't pass the "invariant TSC" feature
> through to guests on my machine even though "invtsc" is set in QEMU
> and the kernel host code appears to support it.  What gives?
> 
> --Andy