From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: Another preempt folding issue? Date: Fri, 14 Feb 2014 18:33:33 +0100 Message-ID: <20140214173333.GA6953@pd.tnic> References: <52FB5669.7090506@canonical.com> <20140212115412.GW27965@twins.programming.kicks-ass.net> <52FCFA23.4060701@canonical.com> <20140213173852.GH6835@laptop.programming.kicks-ass.net> <52FD090C.7010408@canonical.com> <20140213182605.GC14089@laptop.programming.kicks-ass.net> <20140214133428.GB26356@pd.tnic> <52FE2709.3050505@canonical.com> <20140214144700.GC26356@pd.tnic> <52FE4C28.1080500@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Peter Zijlstra , Paolo Bonzini , Linux Kernel Mailing List , kvm@vger.kernel.org, Marcelo Tosatti , MASAO TAKAHASHI , Joerg Roedel To: Stefan Bader Return-path: Content-Disposition: inline In-Reply-To: <52FE4C28.1080500@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Feb 14, 2014 at 06:02:32PM +0100, Stefan Bader wrote: > Okaaay, I think I did what you asked. So yes, there is sse2 in the cpu info. And > there is a mfence in the disassembly: Btw, I just realized booting the kernel in the guest was a dumb idea, because, doh, the guest is not baremetal. The only reliable thing we can say is that sse2 is present and that MFENCE alternative replacement works :) But for simplicity's sake let's just assume the machine can do MFENCE just fine and it gets replaced by the alternatives code. Besides, if that weren't true, we'd have a whole lot of other problems on those boxes. > Thinking about it, I guess Peter is quite right saying that I likely > will end on the patch that converted preempt_count to percpu. Yeah, c2daa3bed53a81171cf8c1a36db798e82b91afe8 et al. > One thing I likely should do is to reinstall the exact same laptop > with 64bit kernel and userspace... maybe only 64bit kernel first... > and make sure on my side that this does not show up on 64bit, too. I > took the word of reporters for that (and the impression that otherwise > many more people would have complained). Yeah, that should be a prudent thing to do. Also, Paolo and I were wondering whether you can trigger this thing without kvm, i.e. virtualization involved... do you have any data on that? Thanks. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --