Path: csiph.com!goblin3!goblin.stu.neva.ru!gandalf.srv.welterde.de!eternal-september.org!feeder.eternal-september.org!aioe.org!bofh.it!news.nic.it!robomod From: Jens Wiklander Newsgroups: linux.kernel Subject: Re: [PATCH v5 1/5] arm/arm64: add smccc ARCH32 Date: Tue, 15 Sep 2015 23:10:01 +0200 Message-ID: References: X-Original-To: Will Deacon X-Google-Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-type:content-disposition:in-reply-to :user-agent; bh=oIhPidXoxhrzLyXzzNom0ImxGaZmP8LHHMtgZ/WPfpI=; b=OlbNsDRusRTTn/hCxOqFAaWKGxPvnn8gplTLmxFymi9vEf54L2EJmSn9/T9qfs5QP0 DiiX79J7M8cNtmE+RG3vJG8T5CzdvwZWA9jzo1A3Awd7ekE+bX2JMUbZmkpe41Tk3ij+ NpGHvdwwaFJy8ZQenEco2+2Jwu30Lk0xq/EjC6kD7tGcYBMeTyDuuF047nVnKGCYYbXS PIyAAFBexEciem/J2Q0HF7v3It8wH8U0Bv3ERfRSJuGkQsSEw6Gv2u8DlEG1jrTthWYv WStyJlUKILE486GovFgO5Vg5/F2mg93eTs4FTSWzl1/AXutd2fskW6GsgoP05HUFYcqb 3irA== X-Gm-Message-State: ALoCoQk5kp3V9ijeoAjA7IyaJlNTKMns9O2MT2eFoj3rK44e+mJ+Bf5RqfvkNkseZ7LWkgEi+pnK X-Received: by 10.194.23.2 with SMTP id i2mr16758138wjf.106.1442351164967; Tue, 15 Sep 2015 14:06:04 -0700 (PDT) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 57 Organization: linux.* mail to news gateway X-Original-Cc: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "devicetree@vger.kernel.org" , Arnd Bergmann , Greg Kroah-Hartman , Kees Cook , "valentin.manea@huawei.com" , Mark Rutland , "javier@javigon.com" , "emmanuel.michel@st.com" , Michal Simek , "jean-michel.delorme@st.com" , Jason Gunthorpe , Rob Herring X-Original-Date: Tue, 15 Sep 2015 23:05:59 +0200 X-Original-Message-ID: <20150915210557.GA31578@ermac> X-Original-References: <1439973629-19505-1-git-send-email-jens.wiklander@linaro.org> <1439973629-19505-2-git-send-email-jens.wiklander@linaro.org> <20150819165009.GC10297@arm.com> <20150820113729.GA25962@ermac> <20150821092430.GC30930@arm.com> <20150821114331.GA11701@ermac> <20150914083029.GA13963@ermac> <20150915182645.GQ31157@arm.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1225548 On Tue, Sep 15, 2015 at 07:26:45PM +0100, Will Deacon wrote: > On Mon, Sep 14, 2015 at 09:30:30AM +0100, Jens Wiklander wrote: > > On Fri, Aug 21, 2015 at 01:43:31PM +0200, Jens Wiklander wrote: > > > On Fri, Aug 21, 2015 at 10:24:30AM +0100, Will Deacon wrote: > > > > On Thu, Aug 20, 2015 at 12:37:29PM +0100, Jens Wiklander wrote: > > > > > On Wed, Aug 19, 2015 at 05:50:09PM +0100, Will Deacon wrote: > > > > > > On Wed, Aug 19, 2015 at 09:40:25AM +0100, Jens Wiklander wrote: > > > > > > > + mov x28, x0 > > > > > > > + ldp w0, w1, [x28, #SMC_PARAM_W0_OFFS] > > > > > > > + ldp w2, w3, [x28, #SMC_PARAM_W2_OFFS] > > > > > > > + ldp w4, w5, [x28, #SMC_PARAM_W4_OFFS] > > > > > > > + ldp w6, w7, [x28, #SMC_PARAM_W6_OFFS] > > > > > > > + smc #0 > > > > > > > + stp w0, w1, [x28, #SMC_PARAM_W0_OFFS] > > > > > > > + stp w2, w3, [x28, #SMC_PARAM_W2_OFFS] > > > > > > > + ldp x28, x30, [sp], #16 > > > > > > > + ret > > > > > > > +ENDPROC(smccc_call32) > > > > > > > > > > > > Could we deal with this like we do for PSCI instead? (see > > > > > > __invoke_psci_fn_smc). We could also then rename psci-call.S to fw-call.S > > > > > > and stick this in there too. > > > > > > > > > > I assume you're referring to when to use "hvc" and "smc". > > > > > > > > No, I mean use a C prototype to avoid marshalling the parameters in assembly > > > > like this. As Rutland pointed out, the return value is a bit messy, but > > > > the arguments align nicely with the PCS afaict. > > > > > > If possible I'd like the function to have the same prototype for both > > > arm and arm64. For arm it's not possible to supply more than 4 > > > parameters. To fully support SMC Calling Convention we need to be able > > > to pass 8 parameters and have 4 return values. The OP-TEE driver in this > > > patch set depends on this. I don't see how we can avoid the marshalling > > > here. > > > > > > We could have two versions of the SMCCC functions, one simplified which > > > only uses registers and one complete like this one with marshalling. > > > > Will, what do think about this? > > I still think you should make use of a C prototype to avoid explicit > parameter marshalling in assembly. If you want to maintain a compatible > API between arm and arm64, then you can easily have an intermediate > function in arm64 that sits between the API entry point and the assembly. Yes, I see how that's convenient for passing argument values in registers, but that doesn't help with storing the returned values in x0..x3 into something accessible in C. Am I missing something? Thanks, Jens -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/