From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH v1 0/5] KVM in-guest performance monitoring Date: Thu, 12 May 2011 15:43:40 +0200 Message-ID: <20110512134339.GH8707@8bytes.org> References: <1305129333-7456-1-git-send-email-avi@redhat.com> <20110512093309.GD8707@8bytes.org> <4DCBACC7.8080000@siemens.com> <20110512131130.GG8707@8bytes.org> <4DCBDF5B.6000101@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo To: Jan Kiszka Return-path: Content-Disposition: inline In-Reply-To: <4DCBDF5B.6000101@siemens.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Thu, May 12, 2011 at 03:23:39PM +0200, Jan Kiszka wrote: > On 2011-05-12 15:11, Joerg Roedel wrote: > > Seriously, I think such decisions should be technical only and not > > political like that. The losers of such political decisions are always > > the users because they don't get useful features that are technical > > possible. > > Paravirt remains a workaround, useful until hardware provides a solution > for all guests, and that often in an even more efficient way (like for > MMU virtualization). Fully agreed. And todays x86 CPUs lack proper support for virtualizing the PMU. That will hopefully change but users want the feature today. > We do not need to block a PV-PMU for Linux guests (or other OSes that > want to adopt to it), but that will not be a solution for the problem, > that's my point. A PV-PMU may even be useful to demonstrate usefulness > of a virtual PMU the CPU vendors (if they aren't aware of this yet). Right, if users actually use the virtual PMU this probably increases the priority for proper hardware support. Joerg