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 X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D096C46470 for ; Wed, 8 Aug 2018 03:25:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24A9F21522 for ; Wed, 8 Aug 2018 03:25:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24A9F21522 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=andestech.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727143AbeHHFm6 (ORCPT ); Wed, 8 Aug 2018 01:42:58 -0400 Received: from exmail.andestech.com ([59.124.169.137]:21899 "EHLO ATCSQR.andestech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726258AbeHHFm6 (ORCPT ); Wed, 8 Aug 2018 01:42:58 -0400 Received: from mail.andestech.com (atcpcs16.andestech.com [10.0.1.222]) by ATCSQR.andestech.com with ESMTP id w783OTNV083368; Wed, 8 Aug 2018 11:24:29 +0800 (GMT-8) (envelope-from alankao@andestech.com) Received: from atcsqa06.andestech.com (10.0.1.85) by ATCPCS16.andestech.com (10.0.1.222) with Microsoft SMTP Server id 14.3.123.3; Wed, 8 Aug 2018 11:25:19 +0800 From: Alan Kao To: , , "Palmer Dabbelt" , Albert Ou , Christoph Hellwig , Andrew Waterman , Arnd Bergmann , Darius Rad CC: Alan Kao , Greentime Hu , Vincent Chen , Zong Li , Nick Hu Subject: [PATCH v4 5/5] Auto-detect whether a FPU exists Date: Wed, 8 Aug 2018 11:24:45 +0800 Message-ID: <1533698685-18022-6-git-send-email-alankao@andestech.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1533698685-18022-1-git-send-email-alankao@andestech.com> References: <1533698685-18022-1-git-send-email-alankao@andestech.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.0.1.85] X-DNSRBL: X-MAIL: ATCSQR.andestech.com w783OTNV083368 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We expect that a kernel with CONFIG_FPU=y can still support no-FPU machines. To do so, the kernel should first examine the existence of a FPU, then do nothing if a FPU does exist; otherwise, it should disable/bypass all FPU-related functions. In this patch, a new global variable, no_fpu, is created and determined when parsing the hardware capability from device tree during booting. This variable is used in those FPU-related functions. Signed-off-by: Alan Kao Cc: Greentime Hu Cc: Vincent Chen Cc: Zong Li Cc: Nick Hu --- arch/riscv/include/asm/hwcap.h | 3 +++ arch/riscv/include/asm/switch_to.h | 13 ++++++++++++- arch/riscv/kernel/cpufeature.c | 11 +++++++++++ arch/riscv/kernel/signal.c | 6 ++++++ 4 files changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 8a4ed7bbcbea..1b870086a869 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -33,5 +33,8 @@ enum { }; extern unsigned long elf_hwcap; +#ifdef CONFIG_FPU +extern bool no_fpu; +#endif #endif #endif diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 093050b03543..7278e3eb7a70 100644 --- a/arch/riscv/include/asm/switch_to.h +++ b/arch/riscv/include/asm/switch_to.h @@ -17,6 +17,7 @@ #include #include #include +#include #ifdef CONFIG_FPU extern void __fstate_save(struct task_struct *save_to); @@ -30,6 +31,9 @@ static inline void __fstate_clean(struct pt_regs *regs) static inline void fstate_save(struct task_struct *task, struct pt_regs *regs) { + if (unlikely(no_fpu)) + return; + if ((regs->sstatus & SR_FS) == SR_FS_DIRTY) { __fstate_save(task); __fstate_clean(regs); @@ -39,6 +43,9 @@ static inline void fstate_save(struct task_struct *task, static inline void fstate_restore(struct task_struct *task, struct pt_regs *regs) { + if (unlikely(no_fpu)) + return; + if ((regs->sstatus & SR_FS) != SR_FS_OFF) { __fstate_restore(task); __fstate_clean(regs); @@ -50,13 +57,17 @@ static inline void __switch_to_aux(struct task_struct *prev, { struct pt_regs *regs; + if (unlikely(no_fpu)) + return; + regs = task_pt_regs(prev); if (unlikely(regs->sstatus & SR_SD)) fstate_save(prev, regs); fstate_restore(next, task_pt_regs(next)); } -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_INITIAL) +#define DEFAULT_SSTATUS \ + ((unlikely(no_fpu)) ? (SR_SPIE | SR_FS_OFF) : (SR_SPIE | SR_FS_INITIAL)) #else #define fstate_save(task, regs) do { } while (0) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17011a870044..bc269c1e0b1a 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -22,6 +22,9 @@ #include unsigned long elf_hwcap __read_mostly; +#ifdef CONFIG_FPU +bool no_fpu __read_mostly; +#endif void riscv_fill_hwcap(void) { @@ -58,4 +61,12 @@ void riscv_fill_hwcap(void) elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; pr_info("elf_hwcap is 0x%lx", elf_hwcap); + +#ifdef CONFIG_FPU + no_fpu = 0; + if (!(elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))) { + pr_info("Bypass FPU code."); + no_fpu = 1; + } +#endif } diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 2450b824d799..9714e4fccb69 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -45,6 +45,9 @@ static long restore_fp_state(struct pt_regs *regs, struct __riscv_d_ext_state __user *state = &sc_fpregs->d; size_t i; + if (unlikely(no_fpu)) + return 0; + err = __copy_from_user(¤t->thread.fstate, state, sizeof(*state)); if (unlikely(err)) return err; @@ -72,6 +75,9 @@ static long save_fp_state(struct pt_regs *regs, struct __riscv_d_ext_state __user *state = &sc_fpregs->d; size_t i; + if (unlikely(no_fpu)) + return 0; + fstate_save(current, regs); err = __copy_to_user(state, ¤t->thread.fstate, sizeof(*state)); if (unlikely(err)) -- 2.18.0