linux-kernel - Re: [PATCH] KVM: x86: fix kvmclock breakage from timers branch merge

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Date:	Fri, 5 Sep 2014 22:41:32 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Paolo Bonzini <pbonzini@...hat.com>
cc:	linux-kernel@...r.kernel.org, chris.j.arges@...onical.com,
	kvm@...r.kernel.org, John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH] KVM: x86: fix kvmclock breakage from timers branch
 merge

On Fri, 5 Sep 2014, Paolo Bonzini wrote:

> Il 05/09/2014 20:33, Thomas Gleixner ha scritto:
> >> >  	update_vsyscall(tk);
> >> > -	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
> >> > 
> >> >  	tk_update_ktime_data(tk);
> >> > +	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
> > Why are you moving the update between vsycall and pvclock update as I
> > did in my patch? We really need to update everything before calling
> > somewhere.
> 
> Do you mean the call should be moved not just after tk_update_ktime_data
> (which sets base_mono), but further down after
> 
>         update_fast_timekeeper(tk);

No, it needs to be above update_vsyscall(). Here is the patch again
which I sent before. [https://lkml.org/lkml/2014/9/5/395]

Thanks,

	tglx

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index fb4a9c2cf8d9..ec1791fae965 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -442,11 +442,12 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action)
 		tk->ntp_error = 0;
 		ntp_clear();
 	}
-	update_vsyscall(tk);
-	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
 
 	tk_update_ktime_data(tk);
 
+	update_vsyscall(tk);
+	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+
 	if (action & TK_MIRROR)
 		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
 		       sizeof(tk_core.timekeeper));
--
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