From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: Re: [Xen-staging] [xen-unstable] Added some more fields to host_cpu. Date: Fri, 02 Mar 2007 13:55:07 -0700 Message-ID: <1172868907.5941.54.camel@bling> References: Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: Jimi Xenidis , xen-devel , ewan@xensource.com, Hollis Blanchard List-Id: xen-devel@lists.xenproject.org On Fri, 2007-03-02 at 20:46 +0000, Keir Fraser wrote: > On 2/3/07 20:39, "Alex Williamson" wrote: > > > On ia64, dom0 doesn't automatically get vcpus for each physical cpu, > > so the first problem is that we're not going to have a /proc/cpuinfo > > entry for every cpu in self.cpus.keys. I think it's likely x86 could > > run into this problem too if a cpu was hotplugged or booted with the > > dom0_max_vcpus options. > > We have indeed hit this problem and I put a patch in this afternoon to > duplicate cpu0's info for any non-existent cpu. Given that the dom0 cpus > could be migrating around on arbitrary physical cpus (even across the > multiple CPUID invocations that the kernel will have made to build the > information for a single 'cpu' in /proc!) this is fine -- x86 multiprocessor > systems are supposed to be symmetric (homogeneous CPUs down to the same > stepping in some cases) anyway. Cool, I see it in staging. This is the approach I used to work around the problem temporarily, but what happens if cpu0 is hot un-plugged? ISTR x86 Linux doesn't support cpu0 hotplug, but on ia64 we can hotplug cpu0. I'd guess powerpc could too. Thanks, Alex -- Alex Williamson HP Open Source & Linux Org.