From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dietmar Hahn Subject: Re: [PATCH 2 of 2] vpmu: Add a vpmu cpuid function Date: Fri, 20 Jan 2012 13:40:19 +0100 Message-ID: <1375017.thPP8t1FNn@amur> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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: Ian Campbell Cc: Wei Wang , Haitao Shan , "xen-devel@lists.xensource.com" , Keir Fraser List-Id: xen-devel@lists.xenproject.org Hi Ian, Am Freitag 20 Januar 2012, 10:54:44 schrieb Keir Fraser: > On 20/01/2012 10:49, "Dietmar Hahn" wrote: > > >> Our CPUID configuration is done per-domain, and from > >> tools/libxc/xc_cpuid_x86.c. CPUID adjustments implemented within the > >> hypervisor are generally not acceptable without very good reason. > > > > Then a way is needed to have access to the opt_vpmu_enabled variable within > > the > > hypervisor from the tools to decide the enabling of the flag (is there such a > > way?) or the mechanism with the boot variable must be changed. > > The opt_vpmu_enabled boot variable was introduced because of a PMU problem in > > the Nehalem cpus leading sometimes to hypervisor crashes. But with the done > > quirk we never had a crash anymore. > > So maybe we can always switch on the vpmu stuff in the hypervisor and add a > > flag in the domain configuration when somebody wants to do some performance > > tests? > > Yes! > > It's obviously an option of fairly narrow interest. If someone tries to > enable the per-domain option on a CPU which has problems, you can fail the > domain creation, or print a warning in the hypervisor log, or whatever. Any > sensible option in that respect is fine by me! What is the best solution for this? A domain specific configuration option is needed (vpmu?) which is usable in libxc/xc_cpuid_x86.c to select/deselect special vpmu bits in the cpuid command. Can you point me to an proper example? Thanks. Dietmar. -- Company details: http://ts.fujitsu.com/imprint.html