From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756047AbcHVPQp (ORCPT ); Mon, 22 Aug 2016 11:16:45 -0400 Received: from mail-oi0-f47.google.com ([209.85.218.47]:33806 "EHLO mail-oi0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754894AbcHVPQm (ORCPT ); Mon, 22 Aug 2016 11:16:42 -0400 Date: Mon, 22 Aug 2016 10:16:40 -0500 From: Andy Gross To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Catalin Marinas , Srinivas Kandagatla , Stephen Boyd , stanimir.varbanov@linaro.org, linux-kernel@vger.kernel.org, patches@linaro.org, Bjorn Andersson , lorenzo.pieralisi@arm.com, sudeep.holla@arm.com Subject: Re: [PATCH 1/2] arm64: kernel: Add SMC Session ID to results Message-ID: <20160822151640.GC30923@hector.attlocal.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160822145326.GK14680@arm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 22, 2016 at 03:53:26PM +0100, Will Deacon wrote: > On Mon, Aug 22, 2016 at 09:02:46AM -0500, Andy Gross wrote: > > On Mon, Aug 22, 2016 at 02:43:14PM +0100, Will Deacon wrote: > > > On Sat, Aug 20, 2016 at 12:51:13AM -0500, Andy Gross wrote: > > > > This patch adds the SMC Session ID to the results passed back from SMC > > > > calls. The Qualcomm SMC implementation provides for interrupted SMC > > > > functions. When this occurs, the SMC call will return a session ID that > > > > is required to be used when resuming the interrupted SMC call. > > > > > > > > Signed-off-by: Andy Gross > > > > --- > > > > arch/arm64/kernel/asm-offsets.c | 1 + > > > > arch/arm64/kernel/smccc-call.S | 1 + > > > > include/linux/arm-smccc.h | 4 +++- > > > > 3 files changed, 5 insertions(+), 1 deletion(-) > > > > > > [...] > > > > > > > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > > > > index b5abfda..82d919f 100644 > > > > --- a/include/linux/arm-smccc.h > > > > +++ b/include/linux/arm-smccc.h > > > > @@ -63,18 +63,20 @@ > > > > /** > > > > * struct arm_smccc_res - Result from SMC/HVC call > > > > * @a0-a3 result values from registers 0 to 3 > > > > + * @a6 Session ID register (optional) > > > > */ > > > > struct arm_smccc_res { > > > > unsigned long a0; > > > > unsigned long a1; > > > > unsigned long a2; > > > > unsigned long a3; > > > > + unsigned long a6; > > > > }; > > > > > > > > /** > > > > * arm_smccc_smc() - make SMC calls > > > > * @a0-a7: arguments passed in registers 0 to 7 > > > > - * @res: result values from registers 0 to 3 > > > > + * @res: result values from registers 0 to 3 and optional register 6 > > > > > > AFAICT from reading the SMCCC spec, parameter register 6 is "Unpredictable, > > > Scratch registers" in return state, so I don't think this is correct. > > > > > > What am I missing? > > > > In the case of Qualcomm's implementation, they return a value in register 6 that > > may or may not be used in subsequent calls. If I want to leverage the arm_smccc > > functions, then I need to extend them to include the optional return value. The > > downside to this is that everyone who uses this is exposed to it. > > Yes, I'm not keen on forcing this behaviour for everybody, as you never > know what other firmware might do with unexpected a6 values. Could we > perhaps quirk it, along the lines of the completely untested patch below? A quirk would work fine. I'll try this out and get back to you. Thanks, Andy > --->8 > > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 05070b72fc28..1895e87d0240 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -141,6 +141,8 @@ int main(void) > #endif > DEFINE(ARM_SMCCC_RES_X0_OFFS, offsetof(struct arm_smccc_res, a0)); > DEFINE(ARM_SMCCC_RES_X2_OFFS, offsetof(struct arm_smccc_res, a2)); > + DEFINE(ARM_SMCCC_RES_QUIRK_ID_OFFS, offsetof(struct arm_smccc_res, quirk.id)); > + DEFINE(ARM_SMCCC_RES_QUIRK_STATE_OFFS, offsetof(struct arm_smccc_res, quirk.state)); > BLANK(); > DEFINE(HIBERN_PBE_ORIG, offsetof(struct pbe, orig_address)); > DEFINE(HIBERN_PBE_ADDR, offsetof(struct pbe, address)); > diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S > index ae0496fa4235..3c6c976eaf5c 100644 > --- a/arch/arm64/kernel/smccc-call.S > +++ b/arch/arm64/kernel/smccc-call.S > @@ -12,6 +12,7 @@ > * > */ > #include > +#include > #include > > .macro SMCCC instr > @@ -20,7 +21,12 @@ > ldr x4, [sp] > stp x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS] > stp x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS] > - ret > + ldr x9, [x4, #ARM_SMCCC_RES_QUIRK_ID_OFFS] > + cbz x9, 1f /* ARM_SMCCC_QUIRK_NONE */ > + cmp x9, #ARM_SMCCC_QUIRK_QCOM_A6 > + b.ne 1f > + str x6, [x4, ARM_SMCCC_RES_QUIRK_STATE_OFFS] > +1: ret > .cfi_endproc > .endm > > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > index b5abfda80465..a3a6e291feb6 100644 > --- a/include/linux/arm-smccc.h > +++ b/include/linux/arm-smccc.h > @@ -14,9 +14,6 @@ > #ifndef __LINUX_ARM_SMCCC_H > #define __LINUX_ARM_SMCCC_H > > -#include > -#include > - > /* > * This file provides common defines for ARM SMC Calling Convention as > * specified in > @@ -60,6 +57,21 @@ > #define ARM_SMCCC_OWNER_TRUSTED_OS 50 > #define ARM_SMCCC_OWNER_TRUSTED_OS_END 63 > > +#define ARM_SMCCC_QUIRK_NONE 0 > +#define ARM_SMCCC_QUIRK_QCOM_A6 1 /* Save/restore register a6 */ > + > +#ifndef __ASSEMBLY__ > + > +#include > +#include > + > +struct arm_smccc_quirk { > + int id; > + union { > + unsigned long a6; > + } state; > +}; > + > /** > * struct arm_smccc_res - Result from SMC/HVC call > * @a0-a3 result values from registers 0 to 3 > @@ -69,6 +81,7 @@ struct arm_smccc_res { > unsigned long a1; > unsigned long a2; > unsigned long a3; > + struct arm_smccc_quirk quirk; > }; > > /** > @@ -101,4 +114,5 @@ asmlinkage void arm_smccc_hvc(unsigned long a0, unsigned long a1, > unsigned long a5, unsigned long a6, unsigned long a7, > struct arm_smccc_res *res); > > +#endif /* !__ASSEMBLY__ */ > #endif /*__LINUX_ARM_SMCCC_H*/ > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html