Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S942262AbcJ0QlZ (ORCPT ); Thu, 27 Oct 2016 12:41:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41400 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936563AbcJ0QlD (ORCPT ); Thu, 27 Oct 2016 12:41:03 -0400 Date: Thu, 27 Oct 2016 18:41:00 +0200 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Laszlo Ersek Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH 0/2] KVM: x86: emulate fxsave and fxrstor Message-ID: <20161027164059.GG4212@potion> References: <20161026205014.19801-1-rkrcmar@redhat.com> <0e5108b0-15f0-56c1-b9e5-626ecff644d7@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0e5108b0-15f0-56c1-b9e5-626ecff644d7@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 27 Oct 2016 16:41:03 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1771 Lines: 41 2016-10-26 23:40+0200, Laszlo Ersek: > On 10/26/16 22:50, Radim Krčmář wrote: >> [1/2] adds the emulation (and could be split into two patches if you'd like), >> [2/2] just refactors the code. >> >> This should fix an issue that users are hitting. Laszlo found several reports: >> - https://bugs.launchpad.net/qemu/+bug/1623276 >> - https://bugzilla.proxmox.com/show_bug.cgi?id=1182 >> - https://bugs.archlinux.org/task/50778 >> >> I have only tested it with a simple kvm-unit-tests, though. Reproducing the >> iPXE issue is on the way ... >> >> >> Radim Krčmář (2): >> KVM: x86: emulate fxsave and fxrstor >> KVM: x86: save one bit in ctxt->d >> >> arch/x86/kvm/emulate.c | 110 ++++++++++++++++++++++++++++++++++++++++++------- >> 1 file changed, 94 insertions(+), 16 deletions(-) >> > > I was just about to post iPXE patches that would disable the FXSAVE / > FXRSTOR instructions in the CONFIG=qemu build (*), but you beat me to it > with the KVM emulation code ;) > > (*) If you look at the iPXE commit that added them, they are a > workaround for a Tivoli VMM bug; i.e., irrelevant for QEMU/KVM guests. > > ... Actually, those iPXE patches that conditionalize FXSAVE / FXRSTOR > may still make sense -- we can rebuild iPXE, and bundle the refreshed > binaries with QEMU v2.7.1, and swiftly at that. Whereas the KVM patches > could take more time to propagate to users?... Not sure. What do you > guys think? This series won't get into 4.9, so it would take almost half a year before the kernel trickles into experimental distros. And updating QEMU/iPXE isn't as dangerous as updating kernel, so I like the idea. I am just tempted to drop a KVM patch with positive diffstat that fixes something that doesn't really need fixing anymore. :)