From nobody Thu May 7 17:41:40 2026 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 1EEBFC433F5 for ; Sun, 22 May 2022 15:44:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348214AbiEVPog (ORCPT ); Sun, 22 May 2022 11:44:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348145AbiEVPob (ORCPT ); Sun, 22 May 2022 11:44:31 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 241723668E for ; Sun, 22 May 2022 08:44:30 -0700 (PDT) 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 B9F89B80AC0 for ; Sun, 22 May 2022 15:44:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83A75C385AA; Sun, 22 May 2022 15:44:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1653234267; bh=issCkMCtvgjOFJMYrAwxjLaKfTsyPKtkpaH6yaHo3nk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q9C/FMqIswh924to3Qp7jaIljZnpLaaKeYqsqusO7vhazCSSbw37NUGB8LKP4PPQX ZK8ILwCXjCulprCDNzK151akWkrgxu/EXjiDxR3WbHklzh95mZ9eRilFL4hP5Qi/rf +XUd0XcDaKl851xKXpDXTcY6vOpuJ8+M1YH7+87AgHfrK7TUoBKVp1svjEVBhrdm4B BdSDgg03pB8l/9bKYCj+dhYrYGLtc+uGi8YauAj2hJeiUphJxcqPemqyOSJ43yo1Er hEoUb/gJCT3CPX1hT6R8XwmXClC1M6Ccvz6KpkFtwzN7NfnTQdXVc6tnFdbZpti+FD sJeu+F5e8pPpQ== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Atish Patra , Anup Patel Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] riscv: introduce unified static key mechanism for ISA extensions Date: Sun, 22 May 2022 23:35:42 +0800 Message-Id: <20220522153543.2656-2-jszhang@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220522153543.2656-1-jszhang@kernel.org> References: <20220522153543.2656-1-jszhang@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Currently, riscv has several extensions which may not be supported on all riscv platforms, for example, FPU and so on. To support unified kernel Image style, we need to check whether the feature is supported or not. If the check sits at hot code path, then performance will be impacted a lot. static key can be used to solve the issue. In the past, FPU support has been converted to use static key mechanism. I believe we will have similar cases in the future. This patch tries to add an unified mechanism to use static keys for some ISA extensions by implementing an array of default-false static keys and enabling them when detected. Signed-off-by: Jisheng Zhang Reviewed-by: Anup Patel Reviewed-by: Atish Patra --- arch/riscv/include/asm/hwcap.h | 25 +++++++++++++++++++++++++ arch/riscv/kernel/cpufeature.c | 7 +++++++ 2 files changed, 32 insertions(+) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 0734e42f74f2..d3e113fe7366 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -12,6 +12,7 @@ #include =20 #ifndef __ASSEMBLY__ +#include /* * This yields a mask that user programs can use to figure out what * instruction set this cpu supports. @@ -55,6 +56,16 @@ enum riscv_isa_ext_id { RISCV_ISA_EXT_ID_MAX =3D RISCV_ISA_EXT_MAX, }; =20 +/* + * This enum represents the logical ID for each RISC-V ISA extension static + * keys. We can use static key to optimize code path if some ISA extensions + * are available. + */ +enum riscv_isa_ext_key { + RISCV_ISA_EXT_KEY_FPU, /* For 'F' and 'D' */ + RISCV_ISA_EXT_KEY_MAX, +}; + struct riscv_isa_ext_data { /* Name of the extension displayed to userspace via /proc/cpuinfo */ char uprop[RISCV_ISA_EXT_NAME_LEN_MAX]; @@ -62,6 +73,20 @@ struct riscv_isa_ext_data { unsigned int isa_ext_id; }; =20 +extern struct static_key_false riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_MAX]; + +static __always_inline int riscv_isa_ext2key(int num) +{ + switch (num) { + case RISCV_ISA_EXT_f: + return RISCV_ISA_EXT_KEY_FPU; + case RISCV_ISA_EXT_d: + return RISCV_ISA_EXT_KEY_FPU; + default: + return -EINVAL; + } +} + unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap); =20 #define riscv_isa_extension_mask(ext) BIT_MASK(RISCV_ISA_EXT_##ext) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 1b2d42d7f589..89f886b35357 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -24,6 +24,8 @@ static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __rea= d_mostly; #ifdef CONFIG_FPU __ro_after_init DEFINE_STATIC_KEY_FALSE(cpu_hwcap_fpu); #endif +__ro_after_init DEFINE_STATIC_KEY_ARRAY_FALSE(riscv_isa_ext_keys, RISCV_IS= A_EXT_KEY_MAX); +EXPORT_SYMBOL(riscv_isa_ext_keys); =20 /** * riscv_isa_extension_base() - Get base extension word @@ -232,6 +234,11 @@ void __init riscv_fill_hwcap(void) print_str[j++] =3D (char)('a' + i); pr_info("riscv: ELF capabilities %s\n", print_str); =20 + for_each_set_bit(i, riscv_isa, RISCV_ISA_EXT_MAX) { + j =3D riscv_isa_ext2key(i); + if (j >=3D 0) + static_branch_enable(&riscv_isa_ext_keys[j]); + } #ifdef CONFIG_FPU if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) static_branch_enable(&cpu_hwcap_fpu); --=20 2.34.1 From nobody Thu May 7 17:41:40 2026 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 0E3BDC433F5 for ; Sun, 22 May 2022 15:44:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348364AbiEVPol (ORCPT ); Sun, 22 May 2022 11:44:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348200AbiEVPob (ORCPT ); Sun, 22 May 2022 11:44:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FD3336B4B for ; Sun, 22 May 2022 08:44:31 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 98FA661003 for ; Sun, 22 May 2022 15:44:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F418DC34113; Sun, 22 May 2022 15:44:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1653234270; bh=lCSXZUmp2XpJTlxqmcLhDoFxLAVPQOfR1UxKkPK1zio=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iOlqu/xxnnOsLiSZ0Z2RlhhRSow89I7Q/7Rj9UuV3DJ5yC9hwu5OxfZck5IMVqYZh 7LVeCtb1iMGpkmSAUm9WRbUp5/wZCI6+bDPk5XCMUHoD5i+wE2VbWfZKcJEbzvl8u0 ctUrihTcckQDZLHkgZogdVFlBRKRBkpsJQVGTAcsBdfs0+ZjxB4pg97bASmweRrRqk 0O1somznEwwm0jU7a52++5Yh4RQpjLhu91a8MN/luOlfnJSbvPOAFpno+gelA+1yyY czDss6+ZiYWfZiP3QVjlbPYLPPxteeWcqlvklTBVVxzYd2hyjTCm6Q8/F+7LyqXZRn I9928bfxSZWTw== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Atish Patra , Anup Patel Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] riscv: switch has_fpu() to the unified static key mechanism Date: Sun, 22 May 2022 23:35:43 +0800 Message-Id: <20220522153543.2656-3-jszhang@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220522153543.2656-1-jszhang@kernel.org> References: <20220522153543.2656-1-jszhang@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This is to use the unified static key mechanism instead of putting static key related here and there. Signed-off-by: Jisheng Zhang Reviewed-by: Anup Patel Reviewed-by: Atish Patra --- arch/riscv/include/asm/switch_to.h | 4 ++-- arch/riscv/kernel/cpufeature.c | 7 ------- 2 files changed, 2 insertions(+), 9 deletions(-) diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/sw= itch_to.h index 0a3f4f95c555..11463489fec6 100644 --- a/arch/riscv/include/asm/switch_to.h +++ b/arch/riscv/include/asm/switch_to.h @@ -8,6 +8,7 @@ =20 #include #include +#include #include #include #include @@ -56,10 +57,9 @@ static inline void __switch_to_aux(struct task_struct *p= rev, fstate_restore(next, task_pt_regs(next)); } =20 -extern struct static_key_false cpu_hwcap_fpu; static __always_inline bool has_fpu(void) { - return static_branch_likely(&cpu_hwcap_fpu); + return static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_FPU]); } #else static __always_inline bool has_fpu(void) { return false; } diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 89f886b35357..0235391be84b 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -21,9 +21,6 @@ unsigned long elf_hwcap __read_mostly; /* Host ISA bitmap */ static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly; =20 -#ifdef CONFIG_FPU -__ro_after_init DEFINE_STATIC_KEY_FALSE(cpu_hwcap_fpu); -#endif __ro_after_init DEFINE_STATIC_KEY_ARRAY_FALSE(riscv_isa_ext_keys, RISCV_IS= A_EXT_KEY_MAX); EXPORT_SYMBOL(riscv_isa_ext_keys); =20 @@ -239,8 +236,4 @@ void __init riscv_fill_hwcap(void) if (j >=3D 0) static_branch_enable(&riscv_isa_ext_keys[j]); } -#ifdef CONFIG_FPU - if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) - static_branch_enable(&cpu_hwcap_fpu); -#endif } --=20 2.34.1