From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [RFT] mmu optimizations branch Date: Tue, 2 Jan 2007 18:02:12 +0100 Message-ID: <20070102170212.GB25271@elte.hu> References: <4598E33B.608@qumranet.com> <20070102161117.GA3306@elte.hu> <459A8909.7020600@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel Return-path: To: Avi Kivity Content-Disposition: inline In-Reply-To: <459A8909.7020600-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org * Avi Kivity wrote: > >unfortunately 0xc011f7f3 is in native_write_msr(), which isnt very > >helpful. (i have CONFIG_PARAVIRT enabled in the -rt guest and host > >kernels) But the MSR values suggest that this is the NMI watchdog > >thing again, trying to program MSR_ARCH_PERFMON_EVENTSEL0 and > >MSR_ARCH_PERFMON_PERFCTR0, but this time Linux recovered due to a > >more robust MSR handling. The guest disabled the NMI watchdog with: > > > > Testing NMI watchdog ... CPU#0: NMI appears to be stuck (0->0)! > > > >the FC6 installer hang that i saw with earlier MMU-branch snapshots > >is fixed. > > > Good. Handling the counter well would have been very difficult, > especially if attempting to support cross migration. as far as the NMI watchdog goes, it's in fact better to keep it disabled this way - it's not like the guest context could 'lock up' in an undebuggable way. Any NMI activity in the guest context would be pretty pointless. I'd suggest simulating a non-working performance counter: i.e. dont inject a #GPF when doing the wrmsr, and maybe preserve the values that were written into the MSR register, but otherwise dont try to implement the functionality by injecting NMIs. Worst-case this could result in user-space debugging tools seeing non-working performance-counter functionality. Ingo ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV