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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEEBFC433EF for ; Thu, 12 May 2022 13:22:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354324AbiELNWZ (ORCPT ); Thu, 12 May 2022 09:22:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354317AbiELNWY (ORCPT ); Thu, 12 May 2022 09:22:24 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7AE6F541B5 for ; Thu, 12 May 2022 06:22:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652361741; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iGoOIUCJGa4SaOfudTG7yQQEUS0BOq99bUpZYAujLo0=; b=WOjP8MdPqu3LOsfahT82zc8xugEfFIT7nCLCVDa+gNXt75X+itV3ea4MPbXhUbiGFqNn1R gopb+V303EGReu1GRKgJA866a/gKyvlz3Iaduty4afXgHptcI2kUeRUl/c+y6typ1h2tzH ac7lB01acVU5UNs6HuDLMrlR6EY+rR8= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-121-T_nAhSk3NPWilPckr5RXCQ-1; Thu, 12 May 2022 09:22:20 -0400 X-MC-Unique: T_nAhSk3NPWilPckr5RXCQ-1 Received: by mail-wm1-f72.google.com with SMTP id g14-20020a1c4e0e000000b0039425ef54d6so1661166wmh.9 for ; Thu, 12 May 2022 06:22:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent :content-language:to:cc:references:from:organization:subject :in-reply-to:content-transfer-encoding; bh=iGoOIUCJGa4SaOfudTG7yQQEUS0BOq99bUpZYAujLo0=; b=M2JcGHXpRHHOsWdDT4nptPPoTcnmzNWdEe+pTUWvZA4YoPmbY0AOEeR62THQ7mE4wj RZoO3L18Ptfo53bZzeeT+/FyXy84l+z/nF22jDp4TAsdCv0XINGnl/MwB7JB0Hh6N8M1 9e71boT+EpOnJDyL3pUCIPReIOZuX4fHvtYZixftIcpSI27W5IRGLwdlR2Rf82rWQwZn Yq2dkOqAKtYLh8x0V4vVweH6SzIF4PNE0z3RzfrcbDAZueaEW4lorpv7sMywvmUFt+0T cFhk3Eie6g/ijf/7VKSJ8HoyyuvGUNgs4b6G2+umcuOm2yAcoEBD9o3ly5tZD7YZtv61 shzA== X-Gm-Message-State: AOAM532F0pqwBIBs4pQNFdm7G1vJor3HNO3YLBYd4+L/vU8tYu9JCDvQ 74JA/QhatZer8E8AHJUWcrmdIk9ADoI6eKOFCqEaOazQwFZ4WoZgf+MpOekK0rsv+d+vWNCX10b xFdhrDcEdFFrnK/cP3WPZaw== X-Received: by 2002:a5d:5746:0:b0:20c:dbc2:397d with SMTP id q6-20020a5d5746000000b0020cdbc2397dmr7981049wrw.658.1652361739078; Thu, 12 May 2022 06:22:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx+hXYu6vzpLOJq39B+H7C8rDVvQP/gQANCQfbt9DiMWxcg2qD5+fl3H5Fdy+4EFw8qj6gfWw== X-Received: by 2002:a5d:5746:0:b0:20c:dbc2:397d with SMTP id q6-20020a5d5746000000b0020cdbc2397dmr7981034wrw.658.1652361738823; Thu, 12 May 2022 06:22:18 -0700 (PDT) Received: from ?IPV6:2003:cb:c701:d200:ee5d:1275:f171:136d? (p200300cbc701d200ee5d1275f171136d.dip0.t-ipconnect.de. [2003:cb:c701:d200:ee5d:1275:f171:136d]) by smtp.gmail.com with ESMTPSA id o11-20020a5d408b000000b0020c9520a940sm4946313wrp.54.2022.05.12.06.22.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 May 2022 06:22:18 -0700 (PDT) Message-ID: <77f6f5e7-5945-c478-0e41-affed62252eb@redhat.com> Date: Thu, 12 May 2022 15:22:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Content-Language: en-US To: Janis Schoetterl-Glausch , Paolo Bonzini , Jonathan Corbet , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Cc: Sven Schnelle , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org References: <20220512131019.2594948-1-scgl@linux.ibm.com> <20220512131019.2594948-2-scgl@linux.ibm.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v3 1/2] KVM: s390: Don't indicate suppression on dirtying, failing memop In-Reply-To: <20220512131019.2594948-2-scgl@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 12.05.22 15:10, Janis Schoetterl-Glausch wrote: > If user space uses a memop to emulate an instruction and that > memop fails, the execution of the instruction ends. > Instruction execution can end in different ways, one of which is > suppression, which requires that the instruction execute like a no-op. > A writing memop that spans multiple pages and fails due to key > protection may have modified guest memory, as a result, the likely > correct ending is termination. Therefore, do not indicate a > suppressing instruction ending in this case. I think that is possibly problematic handling. In TCG we stumbled in similar issues in the past for MVC when crossing page boundaries. Failing after modifying the first page already seriously broke some user space, because the guest would retry the instruction after fixing up the fault reason on the second page: if source and destination operands overlap, you'll be in trouble because the input parameters already changed. For this reason, in TCG we make sure that all accesses are valid before starting modifications. See target/s390x/tcg/mem_helper.c:do_helper_mvc with access_prepare() and friends as an example. Now, I don't know how to tackle that for KVM, I just wanted to raise awareness that injecting an interrupt after modifying page content is possible dodgy and dangerous. -- Thanks, David / dhildenb