From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE92F2AE84; Fri, 21 Mar 2025 15:38:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742571525; cv=none; b=rR9jg1Rdyq5Vvvmn7FOKz9KwDw/mv9JSJujQMpBR9Gy0NbMfsAS2vdz4XJSIau35QTcINO32cO0TFjJJ0E3qjyUjDzjhCNHdCU4ckWQcb6YIEq4+Z0XI8HyJUwDAms0swcGldy50q6XBgb2gbqmttn1LajzKDHnSzzMznGtkExI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742571525; c=relaxed/simple; bh=Hur8klx0pto+bVUCorbe/IOiYL8Zq5fllI2zEDHUVww=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=gUzG2zbqMC9CgfJoiQ3Fj3G5+FFtrbKiILcuceivodvvbU+VynKUAoCxarFwMreuNongjweFPAKdyX5a8egiToMeZePQ5zxj0FEE+t2xcnaW4l597T1ADzxKt/hRZV9gN/k33oJjbStovcJPog4D5oNnm82l2HLuXYyfw6LZnH0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=GJ+56TiP; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="GJ+56TiP" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Hur8klx0pto+bVUCorbe/IOiYL8Zq5fllI2zEDHUVww=; b=GJ+56TiPzAKgxjiUsu7mauybOy n24fB07NZDlX1YLn/Tm3/N4fCjcNUQ9q0RU0sWYbKxHDHcjS49KGgsk2x5WIo4STNXFjF72GtZZpm SmI61QXnTy2B0XeRn/xEReTWMAQ/b/53pzI5qCM0c8RBpEruAa+8A6+Ix6kvZ6n+TAq3+1cxhSwfM O5/74zfEWktOgo18tPoPahIDx4gSX2d0mNRyW6SYmt5eFF1bCXEpsggXvv6AGz9qdAS7bCY5KNges 9SM9ftchBzqBmx35e5D9/mlfno/oC1Xu2k+dxzZDQ8u1EeE8nkQaMzN0i65R/q1YQ0ZVhXIQV2uwm ISYDgY0g==; Received: from [172.31.31.145] (helo=u09cd745991455d.ant.amazon.com) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tveRn-00000004RSj-0sdp; Fri, 21 Mar 2025 15:38:11 +0000 Message-ID: <979b6a34ca5724ced1d4871b58bf227065d7da57.camel@infradead.org> Subject: Using Restricted DMA for virtio-pci From: David Woodhouse To: Claire Chang , Rob Herring , mpe@ellerman.id.au, Joerg Roedel , Will Deacon , Frank Rowand , Konrad Rzeszutek Wilk , boris.ostrovsky@oracle.com, jgross@suse.com, Christoph Hellwig , Marek Szyprowski Cc: heikki.krogerus@linux.intel.com, peterz@infradead.org, benh@kernel.crashing.org, grant.likely@arm.com, paulus@samba.org, mingo@kernel.org, sstabellini@kernel.org, Saravana Kannan , xypron.glpk@gmx.de, "Rafael J . Wysocki" , Bartosz Golaszewski , xen-devel@lists.xenproject.org, Thierry Reding , linux-devicetree , linuxppc-dev@lists.ozlabs.org, Nicolas Boichat , Dan Williams , Andy Shevchenko , Greg KH , Randy Dunlap , lkml , "list@263.net:IOMMU DRIVERS" , Jim Quinlan , Robin Murphy , hch@infradead.org, "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?ISO-8859-1?Q?P=E9rez?= , virtualization@lists.linux.dev, graf@amazon.de Date: Fri, 21 Mar 2025 15:38:10 +0000 In-Reply-To: <20210209062131.2300005-1-tientzu@chromium.org> References: <20210209062131.2300005-1-tientzu@chromium.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-juy7yf7MhQovyScjrs78" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Bad-Reply: References and In-Reply-To but no 'Re:' in Subject. X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html --=-juy7yf7MhQovyScjrs78 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2021-02-09 at 14:21 +0800, Claire Chang wrote: > This series implements mitigations for lack of DMA access control on > systems without an IOMMU, which could result in the DMA accessing the > system memory at unexpected times and/or unexpected addresses, possibly > leading to data leakage or corruption. Replying to an ancient (2021) thread which has already been merged... I'd like to be able to use this facility for virtio devices. Virtio already has a complicated relationship with the DMA API, because there were a bunch of early VMM bugs where the virtio devices where magically exempted from IOMMU protection, but the VMM lied to the guest and claimed they weren't. With the advent of confidential computing, and the VMM (or whatever's emulating the virtio device) not being *allowed* to arbitrarily access all of the guest's memory, the DMA API becomes necessary again. Either a virtual IOMMU needs to determine which guest memory the VMM may access, or the DMA API is wrappers around operations which share/unshare (or unencrypt/encrypt) the memory in question. All of which is complicated and slow, if we're looking at a minimal privileged hypervisor stub like pKVM which enforces the lack of guest memory access from VMM. I'm thinking of defining a new type of virtio-pci device which cannot do DMA to arbitrary system memory. Instead it has an additional memory BAR which is used as a SWIOTLB for bounce buffering. The driver for it would look much like the existing virtio-pci device except that it would register the restricted-dma region first (and thus the swiotlb dma_ops), and then just go through the rest of the setup like any other virtio device. That seems like it ought to be fairly simple, and seems like a reasonable way to allow an untrusted VMM to provide virtio devices with restricted DMA access. While I start actually doing the typing... does anyone want to start yelling at me now? Christoph? mst? :) --=-juy7yf7MhQovyScjrs78 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 aDJAwtycb8yXtILj+TvfhLFhafxroXrflspavejQkEiHjNjtHnwbZ+o43g0/yxjwnarGI3kgcak7 nnI9/8Lqpq79tLHYwLajotwLiGTB71AGN5xK+tzB+D4eN9lXayrjcszgbOv2ZCgzExQUAIt98mre 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