From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch 4/4] KVM: allow direct access to PMTimer port Date: Mon, 26 May 2008 11:03:39 +0300 Message-ID: <483A6EDB.2080905@qumranet.com> References: <20080524234342.983197667@localhost.localdomain> <20080525000036.710955693@localhost.localdomain> <48395C07.1050005@qumranet.com> <20080525161256.GB16012@dmt> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Chris Wright , kvm-devel , Len Brown To: Marcelo Tosatti Return-path: Received: from il.qumranet.com ([212.179.150.194]:24151 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754282AbYEZIDm (ORCPT ); Mon, 26 May 2008 04:03:42 -0400 In-Reply-To: <20080525161256.GB16012@dmt> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: > On Sun, May 25, 2008 at 03:31:03PM +0300, Avi Kivity wrote: > >> Marcelo Tosatti wrote: >> >>> There's not much point in exiting for pmtimer reads, since it runs at a >>> fixed clock rate and its start value is undefined. >>> >>> >> On a migration farm with lots of different hardware, eventually all >> guests will have migrated and none of them will be able to use the >> passthrough port. >> >> What about emulating pmtimer in the host kernel instead of userspace? >> It increases the hit from 1 exit to 3 exits, but they're much faster exits. >> > > I agree, even began writing it, but I think the non-passthrough case > could be optimized later. > But, I claim above that the passthrough case will never be in use on long-running guests due to migration. -- error compiling committee.c: too many arguments to function