From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964824AbcHaOga (ORCPT ); Wed, 31 Aug 2016 10:36:30 -0400 Received: from foss.arm.com ([217.140.101.70]:34140 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933960AbcHaOg1 (ORCPT ); Wed, 31 Aug 2016 10:36:27 -0400 Date: Wed, 31 Aug 2016 15:36:29 +0100 From: Will Deacon To: Andy Gross Cc: Lorenzo Pieralisi , Stephen Boyd , linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Catalin Marinas , Srinivas Kandagatla , stanimir.varbanov@linaro.org, linux-kernel@vger.kernel.org, patches@linaro.org, Bjorn Andersson , sudeep.holla@arm.com Subject: Re: [PATCH 1/2] arm64: kernel: Add SMC Session ID to results Message-ID: <20160831143629.GD29505@arm.com> References: <1471672274-19317-1-git-send-email-andy.gross@linaro.org> <1471672274-19317-2-git-send-email-andy.gross@linaro.org> <20160822134313.GJ14680@arm.com> <20160822140246.GA30923@hector.attlocal.net> <20160822145326.GK14680@arm.com> <20160823003831.GN6502@codeaurora.org> <20160823103841.GD8724@red-moon> <20160830201642.GD24683@hector.attlocal.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160830201642.GD24683@hector.attlocal.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 30, 2016 at 03:16:42PM -0500, Andy Gross wrote: > On Tue, Aug 23, 2016 at 11:38:41AM +0100, Lorenzo Pieralisi wrote: > > On Mon, Aug 22, 2016 at 05:38:31PM -0700, Stephen Boyd wrote: > > > > [...] > > > > > This all comes about because the firmware generates a session id > > > for the SMC call and jams it in x6. The assembly on the > > > non-secure side is written with a tight loop around the smc > > > instruction so that when the return value indicates > > > "interrupted", x6 is kept intact and the non-secure OS can jump > > > back to the secure OS without register reloading. Perhaps > > > referring to x6 as result value is not correct because it's > > > really a session id that's irrelevant once the smc call > > > completes. > > > > Sorry I missed this bit. The session id is _generated_ by secure > > firmware (probably only when the value passed in x6 == 0 (?)) > > and actually returned to the caller so that subsequent (interrupted) > > calls can re-issue the same value, is that correct ? > > > > If that's the case the value in x6 is a result value from an SMCCC > > perspective and your current FW is not SMCCC compliant. > > > > So is Will's solution to this ok? If so I will respin with the minor change to > get it working and resend. If not, do I roll my own smccc wrapper? Obviously I'm biased, but I prefer to handle this as a quirk to make it clear that it's a vendor-specific extension to the SMCCC, so if you could post a patch based on the diff I sent, that would be great. You'll also need to: (1) Make sure you don't break 32-bit ARM (2) Make sure that struct arm_smccc_res is always zero-initialised by its other users (to ensure that QUIRK_NONE is set). In fact, it might be nicer to pass the quirk structure as a separate argument, rather than embed it in arm_smccc_res. Will