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=-0.8 required=3.0 tests=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 0CDEBC433FF for ; Sun, 11 Aug 2019 08:42:49 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D2CF72085B for ; Sun, 11 Aug 2019 08:42:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2CF72085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 853EFAE0; Sun, 11 Aug 2019 08:42:48 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id D5798ACC for ; Sun, 11 Aug 2019 08:42:47 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-qt1-f196.google.com (mail-qt1-f196.google.com [209.85.160.196]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 4BA36786 for ; Sun, 11 Aug 2019 08:42:47 +0000 (UTC) Received: by mail-qt1-f196.google.com with SMTP id d17so21066866qtj.8 for ; Sun, 11 Aug 2019 01:42:47 -0700 (PDT) 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=OwTyRG3c0uWeDZrJY6ZpPNgUs/dENdNyzYLQJF235ng=; b=YcdXVF15dGkjSO1tI5ISMyqDVgXuq6Hk5QlPTcQQokpHwimZGW+BV0Dp8laGmnNVxp AWlpMIdztOtjamW4wx0glQwKmgOd/ES3reVAZnf3+xl5n6whY23LvBkKjtVcbFlKWk1T ArakcQGdGfgL46fxbqq1ZD1kfvJ+DPxWAKLc6kRE3lBEc+Z3gQX3UTqeDKnflDcsetib H6ClH3WS1fPK6jzdjRyTcfm8kBSLjUmtm4Rdir5bEOVg9ImXNbPE2k9sO6fQofxNP7Sl KzYi5eLwqTYi9KZFAxpxNv7NHu1bZg6gADkMig4IKw3U9O1RqkFLpPUMsvrWV37z6xdW l3QA== X-Gm-Message-State: APjAAAVxkvNzVzoMQ+ybAOu2TIbEwD4bXIDeDqZwkoHaweNK39n09OU3 BKtXq5WHPmoOJCtPb4ofVBHcOg== X-Google-Smtp-Source: APXvYqzuHJ2U68lDoEL7EBgwf3NbWFXfC318bVrfWPFs3lvkcljrjOCTNgmV+LGovkQ0nKOOObqhmg== X-Received: by 2002:a0c:ae6d:: with SMTP id z42mr25654119qvc.8.1565512966475; Sun, 11 Aug 2019 01:42:46 -0700 (PDT) Received: from redhat.com (bzq-79-181-91-42.red.bezeqint.net. [79.181.91.42]) by smtp.gmail.com with ESMTPSA id m5sm42472030qkb.117.2019.08.11.01.42.41 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sun, 11 Aug 2019 01:42:45 -0700 (PDT) Date: Sun, 11 Aug 2019 04:42:38 -0400 From: "Michael S. Tsirkin" To: Christoph Hellwig Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190811041636-mutt-send-email-mst@kernel.org> References: <87zhrj8kcp.fsf@morokweng.localdomain> <20190810143038-mutt-send-email-mst@kernel.org> <20190810220702.GA5964@ram.ibm.com> <20190811055607.GA12488@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190811055607.GA12488@lst.de> Cc: Benjamin Herrenschmidt , Jason Wang , Alexey Kardashevskiy , Ram Pai , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Paul Mackerras , iommu@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org, David Gibson X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Sun, Aug 11, 2019 at 07:56:07AM +0200, Christoph Hellwig wrote: > And once again this is entirely going in the wrong direction. The only > way using the DMA API is going to work at all is if the device is ready > for it. So the point made is that if DMA addresses are also physical addresses (not necessarily the same physical addresses that driver supplied), then DMA API actually works even though device itself uses CPU page tables. To put it in other terms: it would be possible to make all or part of memory unenecrypted and then have virtio access all of it. SEV guests at the moment make a decision to instead use a bounce buffer, forcing an extra copy but gaining security. -- MST _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu