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Message-ID: <CAGM2rea50hAAa2L2_zPYgY6-08eTMWVRjoP_KAZpRg21TEd11Q@mail.gmail.com>
Date: Tue, 17 Jul 2018 21:59:15 -0400
From: Pavel Tatashin <pasha.tatashin@...cle.com>
To: boris.ostrovsky@...cle.com
Cc: Steven Sistare <steven.sistare@...cle.com>,
Daniel Jordan <daniel.m.jordan@...cle.com>,
linux@...linux.org.uk, schwidefsky@...ibm.com,
Heiko Carstens <heiko.carstens@...ibm.com>,
John Stultz <john.stultz@...aro.org>, sboyd@...eaurora.org,
x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
douly.fnst@...fujitsu.com, peterz@...radead.org, prarit@...hat.com,
feng.tang@...el.com, Petr Mladek <pmladek@...e.com>,
gnomes@...rguk.ukuu.org.uk, linux-s390@...r.kernel.org,
jgross@...e.com
Subject: Re: [PATCH v13 07/18] x86/xen/time: output xen sched_clock time from 0
> > +static u64 xen_sched_clock(void)
> > +{
> > + return xen_clocksource_read() - xen_sched_clock_offset;
> > +}
>
>
> Should other invocations of xen_clocksource_read() also be offset?
>
I do not believe so. Look in arch/x86/kernel/kvmclock.c
kvm_clock_get_cycles() is not normalized for instance. We need to
normalize kvm_sched_clock_read() and xen_sched_clock(), because it is
used by printk() as a sched_clock() prefix. So not to be confusing we
print time starting from 0, but the other instances where
xen_clocksource_read() is used do not need that.
Thank you,
Pavel
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