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=-7.6 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=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 A2992C433B4 for ; Tue, 18 May 2021 16:22:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79112611CE for ; Tue, 18 May 2021 16:22:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350563AbhERQYN (ORCPT ); Tue, 18 May 2021 12:24:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:50770 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344626AbhERQYF (ORCPT ); Tue, 18 May 2021 12:24:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621354966; 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=f5RJYPLqAYSF7PeEx+nR3RgNKQgQ5XhiMT8l2SDsZYU=; b=EI8iLG7gQ7KvpkzYNTLm9uCaHfPTJoQn5dw2b/M8xuS1bLttR+5TYdszDBzSWOQ4T/xz4Z mKhOV7QWjR45G0LC/RyeblgJyn2DiLO5XdxaZUek4MJab4vwQXbhqEgy/hdwfybKcuwXzk nLWv3hmrAsWW+vKZB5Wjul49TLs7g58= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-154-GmEIuGpkPGypUM95VLL5WQ-1; Tue, 18 May 2021 12:22:45 -0400 X-MC-Unique: GmEIuGpkPGypUM95VLL5WQ-1 Received: by mail-wr1-f70.google.com with SMTP id 22-20020adf82960000b02901115ae2f734so5807827wrc.5 for ; Tue, 18 May 2021 09:22:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=f5RJYPLqAYSF7PeEx+nR3RgNKQgQ5XhiMT8l2SDsZYU=; b=nBke4+FHpG6hPF1d4j163ap/av9cOOwjlKwxk+ZMWlFBlj2fe9O3PZDant+JeKvFvD sF1vtr3IexPczJa0S6TeF3Yho9Mwxp/tTN8jOCHyzHW3v/O2E545MvCQrRc9w2JS/IZ/ uibKZaf76b9rimpfhc+9QtKhvNCkzQrJ6iFLvSXt8ob9APJO058chR3s2WslaABX/k6C MJx9BwUSKqda2XAWT7m5HrkXnu7ZZ64se1NhUtouVOTCbHieY0y96pjlRHl1OvIl+o1W UgsdWNi3jvB9t9c61ZsWkp66NpxT2KA5WO0zz8BA8Aoh9tECfJvbNQt+VIJucubIs20r xFJA== X-Gm-Message-State: AOAM530jIDU6vuFf2I6YYsR4AFw3IKevGDGLLHVlvGskcjHwajLxTBtN pUjr8Lre8Gb3fDqVcBCHuSb7DQGcTeMWyiOhcwhj2n08AbDoL9MnqZ+yGEVsLd/rZ/Bw9/ksOSX baTxXHqOxIHWjMrtbC5W1Zg== X-Received: by 2002:a05:6000:1368:: with SMTP id q8mr8169208wrz.342.1621354963255; Tue, 18 May 2021 09:22:43 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzJXTyLbbe+j8G/6H/hwqiNFjexjmfC5GXKyFTrPfr1NMUTkplW/NkFtTn2Aiu3BABVg2Cz+Q== X-Received: by 2002:a05:6000:1368:: with SMTP id q8mr8169190wrz.342.1621354963029; Tue, 18 May 2021 09:22:43 -0700 (PDT) Received: from [192.168.3.132] (p5b0c64fd.dip0.t-ipconnect.de. [91.12.100.253]) by smtp.gmail.com with ESMTPSA id f7sm17857348wmq.30.2021.05.18.09.22.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 May 2021 09:22:42 -0700 (PDT) Subject: Re: [PATCH v1 00/11] KVM: s390: pv: implement lazy destroy To: Claudio Imbrenda , Cornelia Huck Cc: kvm@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210517200758.22593-1-imbrenda@linux.ibm.com> <20210518170537.58b32ffe.cohuck@redhat.com> <20210518173624.13d043e3@ibm-vm> <20210518180411.4abf837d.cohuck@redhat.com> <20210518181922.52d04c61@ibm-vm> From: David Hildenbrand Organization: Red Hat Message-ID: Date: Tue, 18 May 2021 18:22:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210518181922.52d04c61@ibm-vm> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 18.05.21 18:19, Claudio Imbrenda wrote: > On Tue, 18 May 2021 18:04:11 +0200 > Cornelia Huck wrote: > >> On Tue, 18 May 2021 17:36:24 +0200 >> Claudio Imbrenda wrote: >> >>> On Tue, 18 May 2021 17:05:37 +0200 >>> Cornelia Huck wrote: >>> >>>> On Mon, 17 May 2021 22:07:47 +0200 >>>> Claudio Imbrenda wrote: >> >>>>> This means that the same address space can have memory >>>>> belonging to more than one protected guest, although only one >>>>> will be running, the others will in fact not even have any >>>>> CPUs. >>>> >>>> Are those set-aside-but-not-yet-cleaned-up pages still possibly >>>> accessible in any way? I would assume that they only belong to >>>> the >>> >>> in case of reboot: yes, they are still in the address space of the >>> guest, and can be swapped if needed >>> >>>> 'zombie' guests, and any new or rebooted guest is a new entity >>>> that needs to get new pages? >>> >>> the rebooted guest (normal or secure) will re-use the same pages of >>> the old guest (before or after cleanup, which is the reason of >>> patches 3 and 4) >> >> Took a look at those patches, makes sense. >> >>> >>> the KVM guest is not affected in case of reboot, so the userspace >>> address space is not touched. >> >> 'guest' is a bit ambiguous here -- do you mean the vm here, and the >> actual guest above? >> > > yes this is tricky, because there is the guest OS, which terminates or > reboots, then there is the "secure configuration" entity, handled by the > Ultravisor, and then the KVM VM > > when a secure guest reboots, the "secure configuration" is dismantled > (in this case, in a deferred way), and the KVM VM (and its memory) is > not directly affected > > what happened before was that the secure configuration was dismantled > synchronously, and then re-created. > > now instead, a new secure configuration is created using the same KVM > VM (and thus the same mm), before the old secure configuration has been > completely dismantled. hence the same KVM VM can have multiple secure > configurations associated, sharing the same address space. > > of course, only the newest one is actually running, the other ones are > "zombies", without CPUs. > Can a guest trigger a DoS? -- Thanks, David / dhildenb