From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: Re: LAPIC soft-disable vs. LVT masking Date: Mon, 20 Oct 2008 19:31:58 +0800 Message-ID: <20081020113158.GA30536@yukikaze> References: <48FC4607.10803@siemens.com> <200810201746.35506.sheng.yang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Yang, Sheng" , kvm-devel To: Jan Kiszka Return-path: Received: from ti-out-0910.google.com ([209.85.142.184]:33044 "EHLO ti-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753442AbYJTLcR (ORCPT ); Mon, 20 Oct 2008 07:32:17 -0400 Received: by ti-out-0910.google.com with SMTP id b6so816124tic.23 for ; Mon, 20 Oct 2008 04:32:14 -0700 (PDT) Content-Disposition: inline In-Reply-To: <200810201746.35506.sheng.yang@intel.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Oct 20, 2008 at 05:46:35PM +0800, Yang, Sheng wrote: > On Monday 20 October 2008 16:49:11 Jan Kiszka wrote: > > Hi Sheng, > > > > obviously, I meditated too long over the APIC specs and VAPIC code of > > KVM: When the guest resets the soft-enable bit in SVR, the in-kernel > > APIC implementation also set the LVT masked bits - so far, so fine > > (according to specs). But I failed to read out of that doc if those mask > > bits are permanently set (until the guest clears them again) or only > > until the soft-disabling ends (ie. they are restored to their previous > > state - QEMU goes this way). Can you clarify? > > > > Thanks, > > Jan > > > Hi Jan > > I also can't find related info in the spec. But I think, when software enable > bit is cleaned, the spec said the mask bits are set, which means the content > of register is changed. And no words for what happen if set software enable > bit, so I think it maybe retain the mask state after software enable (a > little more possibility). > > I will give a update if I got more infos. Find some info: SDM 3A 8.5.1 Local Vector Table Mask: [...] This flag would remain set until software clears it. I think this can explain it. If you got some interesting circumstance, please share with us. :) -- regards Yang, Sheng