From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BBCA4C3A59E for ; Wed, 21 Aug 2019 21:15:07 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8F102206DD for ; Wed, 21 Aug 2019 21:15:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F102206DD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35118 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0Xwf-0001R4-OK for qemu-devel@archiver.kernel.org; Wed, 21 Aug 2019 17:15:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40117) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0XdO-0002KK-4m for qemu-devel@nongnu.org; Wed, 21 Aug 2019 16:55:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i0XTu-0006Yn-Pl for qemu-devel@nongnu.org; Wed, 21 Aug 2019 16:45:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59248) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i0XTu-0006VS-H7 for qemu-devel@nongnu.org; Wed, 21 Aug 2019 16:45:22 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C162430833CB; Wed, 21 Aug 2019 20:45:20 +0000 (UTC) Received: from localhost (ovpn-116-73.gru2.redhat.com [10.97.116.73]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4202B5C21A; Wed, 21 Aug 2019 20:45:20 +0000 (UTC) Date: Wed, 21 Aug 2019 17:45:18 -0300 From: Eduardo Habkost To: "owen.si@ucloud.cn" Message-ID: <20190821204518.GG7077@habkost.net> References: <20190819100924.14968-1-owen.si@ucloud.cn> <20190820212306.GM3908@habkost.net> <2019082111044638341815@ucloud.cn> <20190821111934.GO3908@habkost.net> <2019082119541665112723@ucloud.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2019082119541665112723@ucloud.cn> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Wed, 21 Aug 2019 20:45:20 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] Revert "i386: correct cpu_x86_cpuid(0xd)" X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Aug 21, 2019 at 07:54:17PM +0800, owen.si@ucloud.cn wrote: > It is CentOS 6.3 with kernel version 2.6.32-279. Actually all CentOS 6 releases have this issue. We stopped supporting CentOS 6 in July 2016 (2 years after CentOS 7 was released). Be aware that even if we work around that specific bug, there are no guarantees that QEMU will still build on a CentOS 6 host in the future. That said, I probably wouldn't reject a patch that works around that CentOS 6 bug, if it's conditional on kvm_enabled() and has a comment explaining why the workaround exists. > > > > owen.si@ucloud.cn > > From: Eduardo Habkost > Date: 2019-08-21 19:19 > To: owen.si@ucloud.cn > CC: qemu-devel > Subject: Re: Re: [Qemu-devel] [PATCH] Revert "i386: correct cpu_x86_cpuid(0xd)" > On Wed, Aug 21, 2019 at 11:04:46AM +0800, owen.si@ucloud.cn wrote: > > Thanks for you reply, we have some hosts running with legacy kernel, difficult to upgrade, and i want to run the latest qemu. > > Does QEMU support running with legacy kernel(kvm) in design? > > For KVM, QEMU requires Linux 4.5 or newer. See "System > requirements" / "KVM kernel module" section on qemu-doc. We also > aim to support the latest version of Linux distributions with > long term support (e.g. RHEL, Debian, Ubuntu LTS, SLES). > > Do you have more details on the kernel you are using? Is it > built and distributed by a third party? > > > > > > > > > > owen.si@ucloud.cn > > > > From: Eduardo Habkost > > Date: 2019-08-21 05:23 > > To: Bingsong Si > > CC: qemu-devel > > Subject: Re: [Qemu-devel] [PATCH] Revert "i386: correct cpu_x86_cpuid(0xd)" > > On Mon, Aug 19, 2019 at 06:09:24PM +0800, Bingsong Si wrote: > > > This reverts commit de2e68c902f7b6e438b0fa3cfedd74a06a20704f. > > > > > > Initial value of env->xcr0 == 0, then CPUID(EAX=0xd,ECX=0).EBX == 0, after kvm > > > upstream commit 412a3c41, It is ok. > > > On host before commit 412a3c41, some legacy guest, i.e. CentOS 6, get > > > xstate_size == 0, will crash the guest. > > > > > > Signed-off-by: Bingsong Si > > > > cpu_x86_cpuid() is also used by TCG, and needs to return the > > correct data depending on xcr0. If you want to work around a KVM > > bug by ignoring xcr0, it needs to be conditional on > > kvm_enabled(). > > > > But even if we you make this conditional on kvm_enabled(), I > > don't understand why QEMU would need a workaround for a KVM bug > > that was fixed more than 4 years ago. > > > > > --- > > > target/i386/cpu.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > > > index ff65e11008..69562e21ed 100644 > > > --- a/target/i386/cpu.c > > > +++ b/target/i386/cpu.c > > > @@ -4416,7 +4416,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, > > > *ecx = xsave_area_size(x86_cpu_xsave_components(cpu)); > > > *eax = env->features[FEAT_XSAVE_COMP_LO]; > > > *edx = env->features[FEAT_XSAVE_COMP_HI]; > > > - *ebx = xsave_area_size(env->xcr0); > > > + *ebx = *ecx; > > > } else if (count == 1) { > > > *eax = env->features[FEAT_XSAVE]; > > > } else if (count < ARRAY_SIZE(x86_ext_save_areas)) { > > > -- > > > 2.22.0 > > > > > > > > > > -- > > Eduardo > > -- > Eduardo -- Eduardo