From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH] use upstream cpuid code Date: Mon, 3 Aug 2009 11:12:32 -0300 Message-ID: <20090803141232.GD4374@poweredge.glommer> References: <1248811515-6877-1-git-send-email-glommer@redhat.com> <4A76D0BB.3080000@redhat.com> <20090803132226.GC4374@poweredge.glommer> <4A76EEE4.5090403@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx2.redhat.com ([66.187.237.31]:36284 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754924AbZHCOF3 (ORCPT ); Mon, 3 Aug 2009 10:05:29 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n73E5UPQ003028 for ; Mon, 3 Aug 2009 10:05:30 -0400 Content-Disposition: inline In-Reply-To: <4A76EEE4.5090403@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Aug 03, 2009 at 05:06:28PM +0300, Avi Kivity wrote: > On 08/03/2009 04:22 PM, Glauber Costa wrote: >> On Mon, Aug 03, 2009 at 02:57:47PM +0300, Avi Kivity wrote: >> >>> On 07/28/2009 11:05 PM, Glauber Costa wrote: >>> >>>> use cpuid code from upstream. By doing that, we lose the following snippet >>>> in kvm_get_supported_cpuid(): >>>> >>>> ret |= 1<< 12; /* MTRR */ >>>> ret |= 1<< 16; /* PAT */ >>>> ret |= 1<< 7; /* MCE */ >>>> ret |= 1<< 14; /* MCA */ >>>> >>>> A quick search in mailing lists says this code is not really necessary, and we're >>>> keeping it just for backwards compatibility. This is not that important, because >>>> we'd lose it anyway in the golden day in which we totally merge with qemu. >>>> Anyway, if it do _is_ important, we can send a patch to qemu with it. >>>> >>>> >>> It is important. Please don't introduce regressions (if you do, >>> introduce them in separate patches). The procedure to drop such >>> workarounds for kernel bugs is to verify that major distros have the >>> kernel fixes in their supported kernels. >>> >> Since this was introduced to fix a bug that did not even existed in Windows, >> I can't see what you mean by "distro kernels" here. >> > > If qemu-kvm with this patch works on Fedora 10 (latest kernel) and the > equivalent opensuse and Ubuntu kernels, then we can safely remove the > bug workaround. If not, if we apply the patch we just cause users > needless pain. Again, since it was reported to fix a problem (that did not even existed in the first place) with Windows Vista, I don't really know why shouldn'it it work with any of the Linux guests (since they were not affected, to begin with) However, if you point me to a simple test case, I can definitely test it to make sure no weird condition is taking place.