From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Mon, 09 Nov 2015 17:16:05 +0100 Subject: [PATCH 1/3] xen/arm: introduce xen_read_wallclock In-Reply-To: References: <7480268.6Ff8Mvx46N@wuerfel> Message-ID: <17175481.GKnbuH0F1P@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Monday 09 November 2015 13:53:30 Stefano Stabellini wrote: > On Fri, 6 Nov 2015, Arnd Bergmann wrote: > > I'm not quite sure about how the split between pvclock_wall_clock and > > the delta works. Normally I'd expect that pvclock_wall_clock is the wallclock > > time as it was at boot, while delta is the number of expired nanoseconds > > since boot. However it is unclear why the latter has a longer range > > (539 years starting at boot, rather than 126 years starting in 1970). > > Actually we already have a sec overflow field in struct shared_info on > the hypervisor side, called wc_sec_hi. I just need to make use of it in > Linux. See: > > http://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=xen/include/public/xen.h;hb=HEAD > > Thanks for raising my attention to the problem, Sounds good for Xen on ARM. This same interface is also used on KVM, right? Does the extension also work there? Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 1/3] xen/arm: introduce xen_read_wallclock Date: Mon, 09 Nov 2015 17:16:05 +0100 Message-ID: <17175481.GKnbuH0F1P@wuerfel> References: <7480268.6Ff8Mvx46N@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Stefano Stabellini Cc: xen-devel@lists.xensource.com, Ian.Campbell@citrix.com, linux-arm-kernel@lists.infradead.org, Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Monday 09 November 2015 13:53:30 Stefano Stabellini wrote: > On Fri, 6 Nov 2015, Arnd Bergmann wrote: > > I'm not quite sure about how the split between pvclock_wall_clock and > > the delta works. Normally I'd expect that pvclock_wall_clock is the wallclock > > time as it was at boot, while delta is the number of expired nanoseconds > > since boot. However it is unclear why the latter has a longer range > > (539 years starting at boot, rather than 126 years starting in 1970). > > Actually we already have a sec overflow field in struct shared_info on > the hypervisor side, called wc_sec_hi. I just need to make use of it in > Linux. See: > > http://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=xen/include/public/xen.h;hb=HEAD > > Thanks for raising my attention to the problem, Sounds good for Xen on ARM. This same interface is also used on KVM, right? Does the extension also work there? Arnd