From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [PATCH] KVM: SVM: fix trashing of MSR_TSC_AUX Date: Thu, 7 Jul 2016 14:47:12 +0200 Message-ID: <20160707124712.GE13648@pd.tnic> References: <1467812596-18903-1-git-send-email-pbonzini@redhat.com> <20160706141847.GF7300@pd.tnic> <361b792f-87ce-863d-5098-9a18aadd6379@redhat.com> <20160707104128.GC13648@pd.tnic> <128bb0be-e597-32c0-f113-9fe02c257790@redhat.com> <20160707114717.GD13648@pd.tnic> <8c66c2b5-58fe-7384-31a3-f6f784461ca6@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Eduardo Habkost , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org To: Paolo Bonzini Return-path: Received: from mail.skyhub.de ([78.46.96.112]:46632 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752482AbcGGMr2 (ORCPT ); Thu, 7 Jul 2016 08:47:28 -0400 Content-Disposition: inline In-Reply-To: <8c66c2b5-58fe-7384-31a3-f6f784461ca6@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Jul 07, 2016 at 02:28:29PM +0200, Paolo Bonzini wrote: > Because otherwise you couldn't do live migration from new QEMU + new > kernel to new QEMU + old kernel. QEMU tries to avoid requiring lockstep > upgrades of QEMU and KVM (unlike for example perf). Hmm, ok. About that - and I've asked about it a couple of times already - how would you guys feel about a testing feature to qemu - something I'd love to have with which I can set arbitrary CPUID bits for testing kernels? I.e., something like that: qemu ... -cpu=Opteron_G5,cpuid_leaf=,eax=<..>,ebx=<...>, ...,filter=off The filter=off thing is to disable the checking in x86_cpu_filter_features() so that those arbitrary CPUID leafs are actually simulated to the guest. Would something like that make sense for upstream or should I hack it in locally only? Because it sure does help a lot when testing kernel features for unreleased CPUs but for which the code is already being submitted. And with a qemu feature like that, we could at least smoke-test those a bit. Hmmm? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.