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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BAC8CC433F5 for ; Thu, 10 Feb 2022 18:57:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238999AbiBJS5f (ORCPT ); Thu, 10 Feb 2022 13:57:35 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:41276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239113AbiBJS5f (ORCPT ); Thu, 10 Feb 2022 13:57:35 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DCBD10B7 for ; Thu, 10 Feb 2022 10:57:36 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B8A60B82721 for ; Thu, 10 Feb 2022 18:57:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D286C004E1; Thu, 10 Feb 2022 18:57:30 +0000 (UTC) Date: Thu, 10 Feb 2022 18:57:26 +0000 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Marc Zyngier , Shuah Khan , Shuah Khan , Alan Hayward , Luis Machado , Salil Akerkar , Basant Kumar Dwivedi , Szabolcs Nagy , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH v11 08/40] arm64/sme: Manually encode SME instructions Message-ID: References: <20220207152109.197566-1-broonie@kernel.org> <20220207152109.197566-9-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220207152109.197566-9-broonie@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Mon, Feb 07, 2022 at 03:20:37PM +0000, Mark Brown wrote: > As with SVE rather than impose ambitious toolchain requirements for SME > we manually encode the few instructions which we require in order to > perform the work the kernel needs to do. The instructions used to save > and restore context are provided as assembler macros while those for > entering and leaving streaming mode are done in asm volatile blocks > since they are expected to be used from C. > > We could do the SMSTART and SMSTOP operations with read/modify/write > cycles on SVCR but using the aliases provided for individual field > accesses should be slightly faster. These instructions are aliases for > MSR but since our minimum toolchain requirements are old enough to mean > that we can't use the sX_X_cX_cX_X form and they always use xzr rather > than taking a value like write_sysreg_s() wants we just use .inst. > > Signed-off-by: Mark Brown > --- > arch/arm64/include/asm/fpsimd.h | 25 +++++++++++++ > arch/arm64/include/asm/fpsimdmacros.h | 53 +++++++++++++++++++++++++++ > 2 files changed, 78 insertions(+) > > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h > index cb24385e3632..c90f7f99a768 100644 > --- a/arch/arm64/include/asm/fpsimd.h > +++ b/arch/arm64/include/asm/fpsimd.h > @@ -249,6 +249,31 @@ static inline void sve_setup(void) { } > > #endif /* ! CONFIG_ARM64_SVE */ > > +#ifdef CONFIG_ARM64_SME > + > +static inline void sme_smstart_sm(void) > +{ > + asm volatile(".inst 0xd503437f"); > +} > + > +static inline void sme_smstop_sm(void) > +{ > + asm volatile(".inst 0xd503427f"); > +} > + > +static inline void sme_smstop(void) > +{ > + asm volatile(".inst 0xd503467f"); > +} I think you can use xzr with __msr_s. It would be more consistent if we had some sysregs defined to be used with __msr_s. -- Catalin