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=-7.3 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 9238FC433B4 for ; Fri, 9 Apr 2021 14:19:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68C8F611AE for ; Fri, 9 Apr 2021 14:19:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233601AbhDIOTV (ORCPT ); Fri, 9 Apr 2021 10:19:21 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:58788 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231402AbhDIOTT (ORCPT ); Fri, 9 Apr 2021 10:19:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617977946; 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=e3UH0r2xCKD4o2NrpBi1CrnYYl14AvSTiS+slBUMDUw=; b=bE657FGVNDT1+JF79LvsfKshH+AWPFfNEJmbo5m6MNn+th+RjF8/0nq8JGPsD+KfNOx++9 Xx9x5b5pNOCv/LZXDeZW3T4pdeyqTWpXA7Vuw40eJT7cbZI+rs7hvu9ifXcnr4U5YK0K8r 7RHcwnPUBLzrsGWcLI8xuQNmLg5Uxz0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-582-Cv5cFVeBOO2Qwp9BMdJcpg-1; Fri, 09 Apr 2021 10:19:04 -0400 X-MC-Unique: Cv5cFVeBOO2Qwp9BMdJcpg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 561CF81744F; Fri, 9 Apr 2021 14:19:02 +0000 (UTC) Received: from [10.36.115.11] (ovpn-115-11.ams2.redhat.com [10.36.115.11]) by smtp.corp.redhat.com (Postfix) with ESMTP id 38AA16B8DD; Fri, 9 Apr 2021 14:18:57 +0000 (UTC) Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages To: "Kirill A. Shutemov" Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Jim Mattson , David Rientjes , "Edgecombe, Rick P" , "Kleen, Andi" , "Yamahata, Isaku" , x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Oscar Salvador , Naoya Horiguchi References: <20210402152645.26680-1-kirill.shutemov@linux.intel.com> <20210402152645.26680-8-kirill.shutemov@linux.intel.com> <5e934d94-414c-90de-c58e-34456e4ab1cf@redhat.com> <20210409133347.r2uf3u5g55pp27xn@box> <5ef83789-ffa5-debd-9ea2-50d831262237@redhat.com> <20210409141211.wfbyzflj7ygtx7ex@box.shutemov.name> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <8a845f8e-295b-1445-382c-75277ade45ae@redhat.com> Date: Fri, 9 Apr 2021 16:18:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210409141211.wfbyzflj7ygtx7ex@box.shutemov.name> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.04.21 16:12, Kirill A. Shutemov wrote: > On Fri, Apr 09, 2021 at 03:50:42PM +0200, David Hildenbrand wrote: >>>> 3. Allow selected users to still grab the pages (esp. KVM to fault them into >>>> the page tables). >>> >>> As long as fault leads to non-present PTEs we are fine. Usespace still may >>> want to mlock() some of guest memory. There's no reason to prevent this. >> >> I'm curious, even get_user_pages() will lead to a present PTE as is, no? So >> that will need modifications I assume. (although I think it fundamentally >> differs to the way get_user_pages() works - trigger a fault first, then >> lookup the PTE in the page tables). > > For now, the patch has two step poisoning: first fault in, on the add to > shadow PTE -- poison. By the time VM has chance to use the page it's > poisoned and unmapped from the host userspace. IIRC, this then assumes that while a page is protected, it will remain mapped into the NPT; because, there is no way to remap into NPT later because the pages have already been poisoned. -- Thanks, David / dhildenb