Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754157AbaFRS7o (ORCPT ); Wed, 18 Jun 2014 14:59:44 -0400 Received: from mail-qc0-f172.google.com ([209.85.216.172]:54038 "EHLO mail-qc0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751413AbaFRS7m (ORCPT ); Wed, 18 Jun 2014 14:59:42 -0400 Date: Wed, 18 Jun 2014 14:59:39 -0400 From: "Gabriel L. Somlo" To: Eric Northup Cc: Nadav Amit , Nadav Amit , Paolo Bonzini , gleb@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , the arch/x86 maintainers , Linux Kernel Mailing List , KVM , joro@8bytes.org, mst@redhat.com, agraf@suse.de Subject: Re: [PATCH 3/3] KVM: x86: correct mwait and monitor emulation Message-ID: <20140618185939.GF1695@ERROL.INI.CMU.EDU> References: <1403101176-23664-1-git-send-email-namit@cs.technion.ac.il> <1403101176-23664-4-git-send-email-namit@cs.technion.ac.il> <53A1D921.2090305@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 18, 2014 at 11:30:07AM -0700, Eric Northup wrote: > Quoting Gabriel's post http://www.spinics.net/lists/kvm/msg103792.html : > > [...] > > > E.g., OS X 10.5 *does* check CPUID, and panics if it doesn't find it. > > It needs the MONITOR cpuid flag to be on, *and* the actual > > instructions to work. That was an argument in favor of finding a mechanism to allow (qemu) users to enable an otherwise default-off monitor cpuid flag. We definitely don't want to advertise monitor/mwait availability to guests which would otherwise sanely fail back to a hlt-based idle loop when cpuid tells them monitor/mwait are not available :) However, check my earlier proposal of backing out of monitor/mwait entirely (as it turns out, there's a kernel command line to tell OS X not to use monitor/mwait, which is IMHO vastly preferable to creating "undocumented" KVM hacks :) Thanks much, --Gabriel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/