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,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 4EF73C46464 for ; Thu, 9 Aug 2018 06:27:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07A1921B31 for ; Thu, 9 Aug 2018 06:27:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07A1921B31 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 S1728534AbeHIIun (ORCPT ); Thu, 9 Aug 2018 04:50:43 -0400 Received: from exmail.andestech.com ([59.124.169.137]:52877 "EHLO ATCSQR.andestech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728175AbeHIIum (ORCPT ); Thu, 9 Aug 2018 04:50:42 -0400 Received: from mail.andestech.com (atcpcs16.andestech.com [10.0.1.222]) by ATCSQR.andestech.com with ESMTP id w796QKMV087905; Thu, 9 Aug 2018 14:26:20 +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; Thu, 9 Aug 2018 14:27:14 +0800 From: Alan Kao To: , , "Palmer Dabbelt" , Albert Ou , Christoph Hellwig , Andrew Waterman , Arnd Bergmann , Darius Rad CC: , , , , Alan Kao Subject: [PATCH v5 5/5] Auto-detect whether a FPU exists Date: Thu, 9 Aug 2018 14:26:43 +0800 Message-ID: <1533796003-680-6-git-send-email-alankao@andestech.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1533796003-680-1-git-send-email-alankao@andestech.com> References: <1533796003-680-1-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 w796QKMV087905 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, has_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 | 1 + arch/riscv/include/asm/switch_to.h | 9 +++++---- arch/riscv/kernel/cpufeature.c | 8 ++++++++ arch/riscv/kernel/process.c | 4 +++- arch/riscv/kernel/signal.c | 6 ++++-- 5 files changed, 21 insertions(+), 7 deletions(-) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 8a4ed7bbcbea..b0da2cbfb468 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -33,5 +33,6 @@ enum { }; extern unsigned long elf_hwcap; +extern bool has_fpu; #endif #endif diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 093050b03543..7943f991bd86 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); @@ -56,13 +57,12 @@ static inline void __switch_to_aux(struct task_struct *prev, fstate_restore(next, task_pt_regs(next)); } -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_INITIAL) - +extern bool has_fpu; #else +#define has_fpu false #define fstate_save(task, regs) do { } while (0) #define fstate_restore(task, regs) do { } while (0) #define __switch_to_aux(__prev, __next) do { } while (0) -#define DEFAULT_SSTATUS (SR_SPIE | SR_FS_OFF) #endif extern struct task_struct *__switch_to(struct task_struct *, @@ -72,7 +72,8 @@ extern struct task_struct *__switch_to(struct task_struct *, do { \ struct task_struct *__prev = (prev); \ struct task_struct *__next = (next); \ - __switch_to_aux(__prev, __next); \ + if (has_fpu) \ + __switch_to_aux(__prev, __next); \ ((last) = __switch_to(__prev, __next)); \ } while (0) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17011a870044..46942e635266 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 has_fpu __read_mostly; +#endif void riscv_fill_hwcap(void) { @@ -58,4 +61,9 @@ void riscv_fill_hwcap(void) elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; pr_info("elf_hwcap is 0x%lx", elf_hwcap); + +#ifdef CONFIG_FPU + if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) + has_fpu = true; +#endif } diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 3820d89e2db9..97155aee9e71 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -83,7 +83,9 @@ void show_regs(struct pt_regs *regs) void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { - regs->sstatus = DEFAULT_SSTATUS; + regs->sstatus = SR_SPIE; + if (has_fpu) + regs->sstatus |= SR_FS_INITIAL; regs->sepc = pc; regs->sp = sp; set_fs(USER_DS); diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 2450b824d799..f9b5e7e352ef 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -98,7 +98,8 @@ static long restore_sigcontext(struct pt_regs *regs, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs)); /* Restore the floating-point state. */ - err |= restore_fp_state(regs, &sc->sc_fpregs); + if (has_fpu) + err |= restore_fp_state(regs, &sc->sc_fpregs); return err; } @@ -150,7 +151,8 @@ static long setup_sigcontext(struct rt_sigframe __user *frame, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs)); /* Save the floating-point state. */ - err |= save_fp_state(regs, &sc->sc_fpregs); + if (has_fpu) + err |= save_fp_state(regs, &sc->sc_fpregs); return err; } -- 2.18.0