linux-kernel - Re: [GIT PULL RFC] pvclock cleanups and pvclock vsyscall support

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Date:	Thu, 15 Oct 2009 15:51:37 +0900
From:	Avi Kivity <avi@...hat.com>
To:	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	kurt.hackel@...cle.com,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Chris Mason <chris.mason@...cle.com>
Subject: Re: [GIT PULL RFC] pvclock cleanups and pvclock vsyscall support

On 10/15/2009 04:28 AM, Jeremy Fitzhardinge wrote:
> Hi all,
>
> This series contains several things:
>
>   - Unify the separate vdso and vsyscall implementations of vgettimeofday and
>     vgetcpu.  There's at least one bugfix which was only applied to one copy
>     (ignore tcache in vgetcpu was only applied to the vdso version); this
>     should avoid such skews in future.
>
>   - Bug fixes for the Xen and KVM clocksource.read functions to make sure
>     the returned time doesn't regress compared to clocksource.cycle_last.
>     (Probably stable material.)
>
>   - Make sure the pvclock rdtsc is surrounded by appropriate barriers so
>     that it doesn't get speculated to the wrong place with respect to reading
>     the time parameters.  (Probably stable material.)
>
>   - General cleanups of the pvclock algorithm (there's no need to make a local
>     copy of the time parameters before use).
>
>   - Add a new CONFIG_X86_VSYSCALL to control the compilation of vsyscall-related
>     code rather than just using CONFIG_X86_64 - we may want to implement 32-bit
>     vsyscall at some point, and this will make it easier.
>
>   - Add the sched notifier for task migration between CPUs, for use by
>     pvclock vread.
>
>   - Implement a pvclock vread function, so that pvclock-using clocksources can be
>     used by vsyscall/vdso vgettimeofday and vclock_gettime.
>
>   - Use pvclock vread in the Xen clocksource.
>    

Looks good to me.

Acked-by etc.

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

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