From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH 0/8] use jump labels to streamline common APIC configuration Date: Tue, 14 Aug 2012 16:05:54 +0200 Message-ID: <502A5B42.2040102@siemens.com> References: <1344171513-4659-1-git-send-email-gleb@redhat.com> <501E760E.9050109@redhat.com> <20120805133549.GL27579@redhat.com> <501E7839.2030008@redhat.com> <20120805134842.GM27579@redhat.com> <501E7C85.70001@redhat.com> <20120805140305.GN27579@redhat.com> <502A5A16.6040506@siemens.com> <502A5AE0.3080608@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , "kvm@vger.kernel.org" , "mtosatti@redhat.com" To: Avi Kivity Return-path: Received: from goliath.siemens.de ([192.35.17.28]:30149 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190Ab2HNOF5 (ORCPT ); Tue, 14 Aug 2012 10:05:57 -0400 In-Reply-To: <502A5AE0.3080608@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-08-14 16:04, Avi Kivity wrote: > On 08/14/2012 05:00 PM, Jan Kiszka wrote: > >>>> The host can prevent this by leaving disabling the guest pmu. But >>>> disabling jump labels for real-time kernels may be acceptable too. We >>>> can probably to it at run time by forcing the slow path at all times. >>> Yes, it is possible to add module option that will force slow path if >>> needed. >> >> Should I write a patch or will you? Having host-side stop_machine due to >> such common guest operations is indeed a no-go for RT. >> > > Note that an additional patch is needed for perf, otherwise the guest > (or a user, but that's less of a concern for realtime) can easily invoke > stop_machine by configuring and unconfiguring its pmu. Hmm, can't the PMU be blocked by taking away some CPU features? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux