linux-kernel - Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set

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Date:	Wed, 29 May 2013 13:16:38 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	John Stultz <john.stultz@...aro.org>
CC:	<xen-devel@...ts.xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

On 29/05/13 01:18, John Stultz wrote:
> On 05/13/2013 10:56 AM, David Vrabel wrote:
>> From: David Vrabel <david.vrabel@...rix.com>
>>
>> All the virtualized platforms (KVM, lguest and Xen) have persistent
>> wallclocks that have more than one second of precision.
>>
>> read_persistent_wallclock() and update_persistent_wallclock() allow
>> for nanosecond precision but their implementation on x86 with
>> x86_platform.get/set_wallclock() only allows for one second precision.
>> This means guests may see a wallclock time that is off by up to 1
>> second.
>>
>> Make set_wallclock() and get_wallclock() take a struct timespec
>> parameter (which allows for nanosecond precision) so KVM and Xen
>> guests may start with a more accurate wallclock time and a Xen dom0
>> can maintain a more accurate wallclock for guests.
>>
>> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
>> ---
>>   arch/x86/include/asm/mc146818rtc.h |    4 ++--
>>   arch/x86/include/asm/x86_init.h    |    6 ++++--
>>   arch/x86/kernel/kvmclock.c         |    9 +++------
>>   arch/x86/kernel/rtc.c              |   17 +++++++----------
>>   arch/x86/lguest/boot.c             |    4 ++--
>>   arch/x86/platform/efi/efi.c        |   10 ++++++----
>>   arch/x86/xen/time.c                |   19 ++++++-------------
>>   include/linux/efi.h                |    4 ++--
> 
> Just FYI, David: You missed the vrtc code with this conversion.
> 
> I finally got around to pushing my current queue to my public tree and
> the kbuild robot noticed the build failure (required INTEL_MID config to
> trigger).
> 
> The fix I've queued is here:
> https://git.linaro.org/gitweb?p=people/jstultz/linux.git;a=commitdiff;h=52d8e9cc6718ae9e6c44b7723028e4717ba91c8b;hp=1dd5234774b33a17743ae62e8b46b5cd0059e1c7

Oops. Sorry about that.  That fix looks fine.

David
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