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dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33924 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdMl1-0007zP-Kq for qemu-devel@archiver.kernel.org; Tue, 18 Jun 2019 18:39:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53759) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdMkW-0007aO-7P for qemu-devel@nongnu.org; Tue, 18 Jun 2019 18:38:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hdMkV-0005QH-3n for qemu-devel@nongnu.org; Tue, 18 Jun 2019 18:38:44 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:37272) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hdMkU-0005P5-Me for qemu-devel@nongnu.org; Tue, 18 Jun 2019 18:38:42 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5IMXkMi096658; 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Tue, 18 Jun 2019 22:38:39 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3030.oracle.com with ESMTP id 2t77ymrnrn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 18 Jun 2019 22:38:39 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x5IMccZI010683; Tue, 18 Jun 2019 22:38:38 GMT Received: from [10.141.197.71] (/10.141.197.71) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 18 Jun 2019 15:38:38 -0700 To: Paolo Bonzini , Liran Alon References: <20190615004256.16367-1-pbonzini@redhat.com> <20190615004256.16367-4-pbonzini@redhat.com> <0144E234-98F2-4D05-B2AB-8DA23E418D46@oracle.com> <74FC0FAA-54DE-4E72-90F5-32B0551F1D83@oracle.com> From: Maran Wilson Organization: Oracle Corporation Message-ID: <363a4b01-4538-f45d-3d09-d9206b419587@oracle.com> Date: Tue, 18 Jun 2019 15:38:37 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9292 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906180181 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9292 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906180181 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by userp2130.oracle.com id x5IMXkMi096658 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 156.151.31.86 Subject: Re: [Qemu-devel] [PATCH 3/7] KVM: i386: Add support for KVM_CAP_EXCEPTION_PAYLOAD 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@nongnu.org, Nikita Leshenko Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/17/2019 10:27 AM, Paolo Bonzini wrote: > On 17/06/19 13:34, Liran Alon wrote: >> Putting this all together, in case kernel doesn=E2=80=99t support extr= acting >> nested-state, there is no decent way to know if guest is running >> nested-virtualization. Which means that in theory we always need to >> fail migration in case kernel doesn=E2=80=99t support KVM_CAP_NESTED_S= TATE or >> KVM_CAP_EXCEPTION_PAYLOAD and vCPU is exposed with VMX/SVM >> capability. > For VMX this would be okay because we had a blocker before this series, > and this wouldn't be any worse. I agree it shouldn't be a gating issue for this patch series, but I'd=20 hate to see this discussion thread die off. I'm still pretty interested in hearing whether anyone has any good ideas=20 for how to conclusively determine whether a given L1 VM has created a=20 nested L2 or not when the host is running an older Kernel that doesn't=20 support KVM_CAP_NESTED_STATE. That would be a very useful capability,=20 especially for CSP use cases. If anyone has any suggestions about where=20 to look, I don't mind spending some time digging into it and possibly=20 testing out a few ideas. Again, separate from this particular patch=20 series. So far I've been drawing a blank after Liran pointed out that=20 corner case problems associated with env->cr[4] & CR4_VMXE_MASK. Thanks, -Maran > For SVM we can ignore the case and fix it when we have > KVM_CAP_NESTED_STATE, as again that wouldn't be any worse. > > Paolo > >> I can condition this behaviour with a flag that can be manipulated >> using QMP to allow user to indicate it wishes to migrate guest anyway >> in this case. This however bring me back to the entire discussion I >> had with Dr. David Alan Gilbert on migration backwards compatibility >> in general and the fact that I believe we should have a generic QMP >> command which allows to provide list of VMState subsections that can >> be ignored in migration=E2=80=A6 See: >> https://www.mail-archive.com/qemu-devel@nongnu.org/msg622274.html >> >> Paolo, What are your thoughts on how I would proceed with this?