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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 39B07C17448 for ; Tue, 12 Nov 2019 07:55:16 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 E9C8F222C2 for ; Tue, 12 Nov 2019 07:55:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9C8F222C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=us.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47C0Qm3Y7HzF4Jq for ; Tue, 12 Nov 2019 18:55:12 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=us.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=linuxram@us.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=us.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47C0Mg6Y4wzF4FR for ; Tue, 12 Nov 2019 18:52:31 +1100 (AEDT) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id xAC7qKSs073461 for ; Tue, 12 Nov 2019 02:52:28 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2w7qe3a3rn-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 12 Nov 2019 02:52:28 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 12 Nov 2019 07:52:23 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xAC7qL2s54198442 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 12 Nov 2019 07:52:21 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A3AD05204E; Tue, 12 Nov 2019 07:52:21 +0000 (GMT) Received: from oc0525413822.ibm.com (unknown [9.85.181.122]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 745FA5204F; Tue, 12 Nov 2019 07:52:18 +0000 (GMT) Date: Mon, 11 Nov 2019 23:52:15 -0800 From: Ram Pai To: Paul Mackerras Subject: Re: [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall References: <20191104041800.24527-1-bharata@linux.ibm.com> <20191104041800.24527-8-bharata@linux.ibm.com> <20191111041924.GA4017@oak.ozlabs.ibm.com> <20191112010158.GB5159@oc0525413822.ibm.com> <20191112053836.GB10885@oak.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191112053836.GB10885@oak.ozlabs.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19111207-0008-0000-0000-0000032E4184 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19111207-0009-0000-0000-00004A4D4496 Message-Id: <20191112075215.GD5159@oc0525413822.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-11-12_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=971 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1910280000 definitions=main-1911120072 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Ram Pai Cc: Sukadev Bhattiprolu , cclaudio@linux.ibm.com, kvm-ppc@vger.kernel.org, Bharata B Rao , linux-mm@kvack.org, jglisse@redhat.com, Ram Pai , aneesh.kumar@linux.vnet.ibm.com, paulus@au1.ibm.com, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, hch@lst.de Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Nov 12, 2019 at 04:38:36PM +1100, Paul Mackerras wrote: > On Mon, Nov 11, 2019 at 05:01:58PM -0800, Ram Pai wrote: > > On Mon, Nov 11, 2019 at 03:19:24PM +1100, Paul Mackerras wrote: > > > On Mon, Nov 04, 2019 at 09:47:59AM +0530, Bharata B Rao wrote: > > > > From: Sukadev Bhattiprolu > > > > > > > > Implement the H_SVM_INIT_ABORT hcall which the Ultravisor can use to > > > > abort an SVM after it has issued the H_SVM_INIT_START and before the > > > > H_SVM_INIT_DONE hcalls. This hcall could be used when Ultravisor > > > > encounters security violations or other errors when starting an SVM. > > > > > > > > Note that this hcall is different from UV_SVM_TERMINATE ucall which > > > > is used by HV to terminate/cleanup an SVM. > > > > > > > > In case of H_SVM_INIT_ABORT, we should page-out all the pages back to > > > > HV (i.e., we should not skip the page-out). Otherwise the VM's pages, > > > > possibly including its text/data would be stuck in secure memory. > > > > Since the SVM did not go secure, its MSR_S bit will be clear and the > > > > VM wont be able to access its pages even to do a clean exit. > > > ...skip... > > > > If the ultravisor cleans up the SVM's state on its side and then informs > > the Hypervisor to abort the SVM, the hypervisor will not be able to > > cleanly terminate the VM. Because to terminate the SVM, the hypervisor > > still needs the services of the Ultravisor. For example: to get the > > pages back into the hypervisor if needed. Another example is, the > > hypervisor can call UV_SVM_TERMINATE. Regardless of which ucall > > gets called, the ultravisor has to hold on to enough state of the > > SVM to service that request. > > OK, that's a good reason. That should be explained in the commit > message. > > > The current design assumes that the hypervisor explicitly informs the > > ultravisor, that it is done with the SVM, through the UV_SVM_TERMINATE > > ucall. Till that point the Ultravisor must to be ready to service any > > ucalls made by the hypervisor on the SVM's behalf. > > I see that UV_SVM_TERMINATE is done when the VM is being destroyed (at > which point kvm->arch.secure_guest doesn't matter any more), and in > kvmhv_svm_off(), where kvm->arch.secure_guest gets cleared > explicitly. Hence I don't see any need for clearing it in the > assembly code on the next secure guest entry. I think the change to > book3s_hv_rmhandlers.S can just be dropped. There is subtle problem removing that code from the assembly. If the H_SVM_INIT_ABORT hcall returns to the ultravisor without clearing kvm->arch.secure_guest, the hypervisor will continue to think that the VM is a secure VM. However the primary reason the H_SVM_INIT_ABORT hcall was invoked, was to inform the Hypervisor that it should no longer consider the VM as a Secure VM. So there is a inconsistency there. This is fine, as long as the VM does not invoke any hcall or does not receive any hypervisor-exceptions. The moment either of those happen, the control goes into the hypervisor, the hypervisor services the exception/hcall and while returning, it will see that the kvm->arch.secure_guest flag is set and **incorrectly** return to the ultravisor through a UV_RETURN ucall. Ultravisor will not know what to do with it, because it does not consider that VM as a Secure VM. Bad things happen. ( Sidenote: when H_SVM_INIT_ABORT hcalls returns from the hypervisor, the ultravisor cleans up its internal state corresponding of that aborted-SVM and returns back to the caller with MSR[S]=0 ) RP