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=-8.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2F6D4C8300F for ; Wed, 2 Dec 2020 18:21:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2E2D22249 for ; Wed, 2 Dec 2020 18:21:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387712AbgLBSVS (ORCPT ); Wed, 2 Dec 2020 13:21:18 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:59568 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726283AbgLBSVR (ORCPT ); Wed, 2 Dec 2020 13:21:17 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0B2IAGEP060754; Wed, 2 Dec 2020 18:20:24 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=NvXmPPCGdV/IwlwX5m8biP5G7/GLn4XsbadAGDcm+UM=; b=aiAw6KzZJljLGyousX8MtLMVHd63vVGtR1foBlXW8W0fuHHk2AKDixJYmbwQ5Pil7kwy 0qpdDkeRikZjMEH/vNv5XFOb57gzQDhAdKzpRZMepwCqVsi/VbRAGofkImCr9wXZWqbm NcOdTJmJ7LSNhsQjefYc3uF5eTau2wq83ViDfGa5q9WK1n+R0DywICH3yLVGkZEQ7r5o BweQnoSYe20iiXboQ20a1lUE3gKisul58g2Vxng52y10/Fo7GPMASeRU/FlJ71HNZqe2 U13Y9NdtAqxTjdxltH0OtxcdxcUdduNko70s6cxDEhztIy4B92iqSbcKswOyhThmXhfj TQ== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 353dyqt01w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 02 Dec 2020 18:20:24 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0B2IABEx151364; Wed, 2 Dec 2020 18:20:24 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 3540f0rnrh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 02 Dec 2020 18:20:23 +0000 Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0B2IKLKE003344; Wed, 2 Dec 2020 18:20:21 GMT Received: from [192.168.0.108] (/70.36.60.91) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 02 Dec 2020 10:20:20 -0800 Subject: Re: [PATCH RFC 02/39] KVM: x86/xen: intercept xen hypercalls if enabled To: David Woodhouse , Joao Martins , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Boris Ostrovsky , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org References: <20190220201609.28290-1-joao.m.martins@oracle.com> <20190220201609.28290-3-joao.m.martins@oracle.com> <240b82b3-9621-8b08-6d37-75da6a61b3ce@oracle.com> <684bd330949528ecd352d4a381165c2681c0bae9.camel@infradead.org> From: Ankur Arora Message-ID: <9971be28-8a0f-a108-6d5e-6a891e395b5f@oracle.com> Date: Wed, 2 Dec 2020 10:20:17 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <684bd330949528ecd352d4a381165c2681c0bae9.camel@infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9823 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 malwarescore=0 phishscore=0 suspectscore=0 bulkscore=0 spamscore=0 adultscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012020108 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9823 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 bulkscore=0 clxscore=1015 mlxscore=0 spamscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012020108 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-12-02 12:03 a.m., David Woodhouse wrote: > On Tue, 2020-12-01 at 21:19 -0800, Ankur Arora wrote: >>> + for (i = 0; i < PAGE_SIZE / sizeof(instructions); i++) { >>> + *(u32 *)&instructions[1] = i; >>> + if (kvm_vcpu_write_guest(vcpu, >>> + page_addr + (i * sizeof(instructions)), >>> + instructions, sizeof(instructions))) >>> + return 1; >>> + } >> >> HYPERVISOR_iret isn't supported on 64bit so should be ud2 instead. > > Yeah, I got part way through typing that part but concluded it probably > wasn't a fast path that absolutely needed to be emulated in the kernel. > > The VMM can inject the UD# when it receives the hypercall. That would work as well but if it's a straight ud2 on the hypercall page, wouldn't the guest just execute it when/if it does a HYPERVISOR_iret? Ankur > > I appreciate it *is* a guest-visible difference, if we're being really > pedantic, but I don't think we were even going to be able to 100% hide > the fact that it's not actually Xen. >