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Date: Wed, 15 Jan 2014 14:08:01 +0100
From: =?UTF-8?B?Um9nZXIgUGF1IE1vbm7DqQ==?= <roger.pau@citrix.com>
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To: Julian Stecklina <jsteckli@os.inf.tu-dresden.de>,
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Subject: Re: KVM Clock
References: <lb3jnb$qo8$1@ger.gmane.org> <52D5623C.7060401@freebsd.org>
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On 15/01/14 13:05, Julian Stecklina wrote:
> On 01/14/2014 05:13 PM, Peter Grehan wrote:
>> Hi Julian,
>> 
>>> is anyone working on KVM clock support for FreeBSD? If not, I
>>> might take a shot at it.
>> 
>> None I know of: go for it :)
> 
> Works for me so far: 
> https://github.com/blitz/freebsd/commit/cdc5f872b3e48cc0dda031fc7d6bdedc65c3148f

Looking
> 
at the code it seems some common routines could be shared
between the KVM PV clock and the Xen PV clock
(sys/dev/xen/timer/timer.c). The data passed from the hypervisor to
the guest has exactly the same format (see struct vcpu_time_info in
Xen public headers).

At a first sight the KVM clock can benefit from using scale_delta
(which is going to be faster than the C version implemented in
kvmclock_get_timecount), and xen_fetch_vcpu_tinfo is exactly the same
as kvmclock_fetch.

Roger.