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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 A6DA9C64E7B for ; Mon, 30 Nov 2020 11:18:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DDE9207BC for ; Mon, 30 Nov 2020 11:18:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726197AbgK3LSl (ORCPT ); Mon, 30 Nov 2020 06:18:41 -0500 Received: from foss.arm.com ([217.140.110.172]:52672 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725902AbgK3LSl (ORCPT ); Mon, 30 Nov 2020 06:18:41 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CCB101042; Mon, 30 Nov 2020 03:17:55 -0800 (PST) Received: from bogus (unknown [10.57.62.34]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3F7593F66B; Mon, 30 Nov 2020 03:17:53 -0800 (PST) Date: Mon, 30 Nov 2020 11:17:50 +0000 From: Sudeep Holla To: Jens Wiklander Cc: linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, Trilok Soni , Trilok Soni , arve@android.com, Andrew Walbran , David Hartley , Achin Gupta , Android Kernel Team , Fuad Tabba Subject: Re: [PATCH v2 0/9] firmware: Add initial support for Arm FF-A Message-ID: <20201130111750.uiws2f2neygs7qrg@bogus> References: <20201103174350.991593-1-sudeep.holla@arm.com> <20201128122502.GA8649@jade> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201128122502.GA8649@jade> User-Agent: NeoMutt/20171215 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Sat, Nov 28, 2020 at 01:25:02PM +0100, Jens Wiklander wrote: > Hi Sudeep, > > On Tue, Nov 03, 2020 at 05:43:41PM +0000, Sudeep Holla wrote: > > Hi all, > > > > Let me start stating this is just initial implementation to check on > > the idea of providing more in-kernel and userspace support. Lot of things > > are still work in progress, I am posting just to get the early feedback > > before building lot of things on this idea. Consider this more as RFC > > though not tagged explicity(just to avoid it being ignored :)) > > > > Arm Firmware Framework for Armv8-A specification[1] describes a software > > architecture that provides mechanism to utilise the virtualization > > extension to isolate software images and describes interfaces that > > standardize communication between the various software images. This > > includes communication between images in the Secure and Normal world. > > > > The main idea here is to create FFA device to establish any communication > > with a partition(secure or normal world VM). > > > > If it is a partition managed by hypervisor, then we will register chardev > > associated with each of those partition FFA device. > > > > /dev/arm_ffa: > > > > e3a48fa5-dc54-4a8b-898b-bdc4dfeeb7b8 > > 49f65057-d002-4ae2-b4ee-d31c7940a13d > > > > For in-kernel usage(mostly communication with secure partitions), only > > in-kernel APIs are accessible(no userspace). There may be a need to > > provide userspace access instead of in-kernel, it is not yet support > > in this series as we need way to identify those and I am not sure if > > that belong to DT. > > With unfiltered VM to VM commnication from user space there's no easy > way for two VMs to exchange privileged information that excludes user > space. Though this usercase is dropped now, it was targeted for VMM and may be it was not an issue there. > Perhaps access to the FFA device is considered privileged and > enough for all purposes. > I don't know TBH. > If I've understood it correctly is VM to SP communication only allowed > via kernel mode in the VM. Correct. > The communication with OP-TEE depends on this with the recent commit > c5b4312bea5d ("tee: optee: Add support for session login client UUID > generation"). > OK, thanks for the info. -- Regards, Sudeep