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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D5B59C56202 for ; Wed, 25 Nov 2020 15:57:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68CA820789 for ; Wed, 25 Nov 2020 15:57:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ItNKJVMN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730345AbgKYP5S (ORCPT ); Wed, 25 Nov 2020 10:57:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56630 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730000AbgKYP5R (ORCPT ); Wed, 25 Nov 2020 10:57:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606319836; 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: in-reply-to:in-reply-to:references:references; bh=6UsChBqvJlhq7/VCtB24VhPBOq4VAuCpHpvRtmkDfHo=; b=ItNKJVMNhckgCujx1YJJxkjNMAWWatV4XDBSvp3dDI+9kr+0IYVerntm6hFNuEB0J+Tt5/ hhOUHOvopZZU5lgFzlWlxlWM7co2holyF/7Isku4mPZX/eM6i3ZknRjllfpgCamf0g82jf qeIipI3naKiSnWeB/OeA1TUcArEsa2s= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-387-qyac24KVP9SnpDUIMEGZ-A-1; Wed, 25 Nov 2020 10:57:14 -0500 X-MC-Unique: qyac24KVP9SnpDUIMEGZ-A-1 Received: by mail-qk1-f197.google.com with SMTP id l7so2848367qkl.16 for ; Wed, 25 Nov 2020 07:57:14 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=6UsChBqvJlhq7/VCtB24VhPBOq4VAuCpHpvRtmkDfHo=; b=NNCBLG9MIX0SRYusYtcgqMEx+rIn1/scuBxS71u7RGJwBZVdjoUs5uIwik4fZ8byaI cDJ2TYJO4mwkfGHv/rUyRRVGV08Mmq6TWQWT1sFCyeNZKYG+APKdqkuEGYMcPqR/jGzD VohzoaQrIUNtthKiN5mCrdv11SczoUROxRaxe7IHmmVj1X7xx87j2YC9SRESx+KFkSYg jELS48ZgyQXybjtuVPSnbOUTM3+1uyF0lFQ4/E2VSdsHiB12RyFQpMXQ9EHIN+Vt0u04 ADSHyND5wC+WUop3mgtHzcYYXgGEW7Z0LojTrAkKSHiIWoRX2T10eSh8S1OZV6pGESiq 9T7Q== X-Gm-Message-State: AOAM532evxWZDBy2c56qOvZMYF6NajPaLIS6eNv7lA/K3VJ9jn8DtFGn nc/xwINkD3MtfgpuuRzqH3QOHKo7cdukgkc2cvBsQwIjtzV5IxCa/6wa94CiLCWaxty47nrRB/F ObP7D0JuuTqSy X-Received: by 2002:ac8:3a22:: with SMTP id w31mr3607607qte.361.1606319834458; Wed, 25 Nov 2020 07:57:14 -0800 (PST) X-Google-Smtp-Source: ABdhPJwqXP9dfk5vg012xJp3zY6wCkaEZcvXplSVZ/8UjBZyLOw518QOEPgewUcisXjRkEI7Hyt7UA== X-Received: by 2002:ac8:3a22:: with SMTP id w31mr3607591qte.361.1606319834220; Wed, 25 Nov 2020 07:57:14 -0800 (PST) Received: from xz-x1 ([142.126.81.247]) by smtp.gmail.com with ESMTPSA id d19sm2387953qtd.32.2020.11.25.07.57.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 07:57:13 -0800 (PST) Date: Wed, 25 Nov 2020 10:57:11 -0500 From: Peter Xu To: Justin He Cc: Alex Williamson , Cornelia Huck , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Stefan Hajnoczi Subject: Re: [PATCH] vfio iommu type1: Bypass the vma permission check in vfio_pin_pages_remote() Message-ID: <20201125155711.GA6489@xz-x1> References: <20201119142737.17574-1-justin.he@arm.com> <20201124181228.GA276043@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Nov 25, 2020 at 01:05:25AM +0000, Justin He wrote: > > I'd appreciate if you could explain why vfio needs to dma map some > > PROT_NONE > > Virtiofs will map a PROT_NONE cache window region firstly, then remap the sub > region of that cache window with read or write permission. I guess this might > be an security concern. Just CC virtiofs expert Stefan to answer it more accurately. Yep. Since my previous sentence was cut off, I'll rephrase: I was thinking whether qemu can do vfio maps only until it remaps the PROT_NONE regions into PROT_READ|PROT_WRITE ones, rather than trying to map dma pages upon PROT_NONE. Thanks, -- Peter Xu