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=-15.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 3AF91C4320A for ; Thu, 5 Aug 2021 10:06:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19A1160EE7 for ; Thu, 5 Aug 2021 10:06:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240176AbhHEKGx (ORCPT ); Thu, 5 Aug 2021 06:06:53 -0400 Received: from pegase2.c-s.fr ([93.17.235.10]:39505 "EHLO pegase2.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240012AbhHEKGd (ORCPT ); Thu, 5 Aug 2021 06:06:33 -0400 Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4GgPQJ2Dj8z9sWd; Thu, 5 Aug 2021 12:06:16 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8oyvXudL7BcU; Thu, 5 Aug 2021 12:06:16 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4GgPQJ0jp3z9sWW; Thu, 5 Aug 2021 12:06:16 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id E80428B7BF; Thu, 5 Aug 2021 12:06:15 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 3NbVlcRkN_qF; Thu, 5 Aug 2021 12:06:15 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 01A878B7BD; Thu, 5 Aug 2021 12:06:14 +0200 (CEST) Subject: Re: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register To: sxwjean@me.com, linuxppc-dev@lists.ozlabs.org Cc: oleg@redhat.com, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, ravi.bangoria@linux.ibm.com, npiggin@gmail.com, aneesh.kumar@linux.ibm.com, sandipan@linux.ibm.com, efremov@linux.com, peterx@redhat.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Xiongwei Song References: <20210726143053.532839-1-sxwjean@me.com> From: Christophe Leroy Message-ID: <5e2336aa-90bf-b820-b5e4-e9a63088930f@csgroup.eu> Date: Thu, 5 Aug 2021 12:06:15 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210726143053.532839-1-sxwjean@me.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 26/07/2021 à 16:30, sxwjean@me.com a écrit : > From: Xiongwei Song > > Create an anonymous union for dsisr and esr regsiters, we can reference > esr to get the exception detail when CONFIG_4xx=y or CONFIG_BOOKE=y. > Otherwise, reference dsisr. This makes code more clear. I'm not sure it is worth doing that. What is the point in doing the following when you know that regs->esr and regs->dsisr are exactly the same: > - err = ___do_page_fault(regs, regs->dar, regs->dsisr); > + if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE)) > + err = ___do_page_fault(regs, regs->dar, regs->esr); > + else > + err = ___do_page_fault(regs, regs->dar, regs->dsisr); > + Or even > - int is_write = page_fault_is_write(regs->dsisr); > + unsigned long err_reg; > + int is_write; > + > + if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE)) > + err_reg = regs->esr; > + else > + err_reg = regs->dsisr; > + > + is_write = page_fault_is_write(err_reg); Artificially growing the code for that makes no sense to me. To avoid anbiguity, maybe the best would be to rename regs->dsisr to something like regs->sr , so that we know it represents the status register, which is DSISR or ESR depending on the platform. > > Signed-off-by: Xiongwei Song > --- > arch/powerpc/include/asm/ptrace.h | 5 ++++- > arch/powerpc/include/uapi/asm/ptrace.h | 5 ++++- > arch/powerpc/kernel/process.c | 2 +- > arch/powerpc/kernel/ptrace/ptrace.c | 2 ++ > arch/powerpc/kernel/traps.c | 2 +- > arch/powerpc/mm/fault.c | 16 ++++++++++++++-- > arch/powerpc/platforms/44x/machine_check.c | 4 ++-- > arch/powerpc/platforms/4xx/machine_check.c | 2 +- > 8 files changed, 29 insertions(+), 9 deletions(-) > > diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h > index 3e5d470a6155..c252d04b1206 100644 > --- a/arch/powerpc/include/asm/ptrace.h > +++ b/arch/powerpc/include/asm/ptrace.h > @@ -44,7 +44,10 @@ struct pt_regs > #endif > unsigned long trap; > unsigned long dar; > - unsigned long dsisr; > + union { > + unsigned long dsisr; > + unsigned long esr; > + }; > unsigned long result; > }; > }; > diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h > index 7004cfea3f5f..e357288b5f34 100644 > --- a/arch/powerpc/include/uapi/asm/ptrace.h > +++ b/arch/powerpc/include/uapi/asm/ptrace.h > @@ -53,7 +53,10 @@ struct pt_regs > /* N.B. for critical exceptions on 4xx, the dar and dsisr > fields are overloaded to hold srr0 and srr1. */ > unsigned long dar; /* Fault registers */ > - unsigned long dsisr; /* on 4xx/Book-E used for ESR */ > + union { > + unsigned long dsisr; /* on Book-S used for DSISR */ > + unsigned long esr; /* on 4xx/Book-E used for ESR */ > + }; > unsigned long result; /* Result of a system call */ > }; > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index 185beb290580..f74af8f9133c 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -1499,7 +1499,7 @@ static void __show_regs(struct pt_regs *regs) > trap == INTERRUPT_DATA_STORAGE || > trap == INTERRUPT_ALIGNMENT) { > if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE)) > - pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr); > + pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->esr); > else > pr_cont("DAR: "REG" DSISR: %08lx ", regs->dar, regs->dsisr); > } > diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c > index 0a0a33eb0d28..00789ad2c4a3 100644 > --- a/arch/powerpc/kernel/ptrace/ptrace.c > +++ b/arch/powerpc/kernel/ptrace/ptrace.c > @@ -375,6 +375,8 @@ void __init pt_regs_check(void) > offsetof(struct user_pt_regs, dar)); > BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) != > offsetof(struct user_pt_regs, dsisr)); > + BUILD_BUG_ON(offsetof(struct pt_regs, esr) != > + offsetof(struct user_pt_regs, esr)); > BUILD_BUG_ON(offsetof(struct pt_regs, result) != > offsetof(struct user_pt_regs, result)); > > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c > index dfbce527c98e..2164f5705a0b 100644 > --- a/arch/powerpc/kernel/traps.c > +++ b/arch/powerpc/kernel/traps.c > @@ -562,7 +562,7 @@ static inline int check_io_access(struct pt_regs *regs) > #ifdef CONFIG_PPC_ADV_DEBUG_REGS > /* On 4xx, the reason for the machine check or program exception > is in the ESR. */ > -#define get_reason(regs) ((regs)->dsisr) > +#define get_reason(regs) ((regs)->esr) > #define REASON_FP ESR_FP > #define REASON_ILLEGAL (ESR_PIL | ESR_PUO) > #define REASON_PRIVILEGED ESR_PPR > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index a8d0ce85d39a..62953d4e7c93 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -541,7 +541,11 @@ static __always_inline void __do_page_fault(struct pt_regs *regs) > { > long err; > > - err = ___do_page_fault(regs, regs->dar, regs->dsisr); > + if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE)) > + err = ___do_page_fault(regs, regs->dar, regs->esr); > + else > + err = ___do_page_fault(regs, regs->dar, regs->dsisr); > + > if (unlikely(err)) > bad_page_fault(regs, err); > } > @@ -567,7 +571,15 @@ NOKPROBE_SYMBOL(hash__do_page_fault); > */ > static void __bad_page_fault(struct pt_regs *regs, int sig) > { > - int is_write = page_fault_is_write(regs->dsisr); > + unsigned long err_reg; > + int is_write; > + > + if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE)) > + err_reg = regs->esr; > + else > + err_reg = regs->dsisr; > + > + is_write = page_fault_is_write(err_reg); > > /* kernel has accessed a bad area */ > > diff --git a/arch/powerpc/platforms/44x/machine_check.c b/arch/powerpc/platforms/44x/machine_check.c > index a5c898bb9bab..5d19daacd78a 100644 > --- a/arch/powerpc/platforms/44x/machine_check.c > +++ b/arch/powerpc/platforms/44x/machine_check.c > @@ -11,7 +11,7 @@ > > int machine_check_440A(struct pt_regs *regs) > { > - unsigned long reason = regs->dsisr; > + unsigned long reason = regs->esr; > > printk("Machine check in kernel mode.\n"); > if (reason & ESR_IMCP){ > @@ -48,7 +48,7 @@ int machine_check_440A(struct pt_regs *regs) > #ifdef CONFIG_PPC_47x > int machine_check_47x(struct pt_regs *regs) > { > - unsigned long reason = regs->dsisr; > + unsigned long reason = regs->esr; > u32 mcsr; > > printk(KERN_ERR "Machine check in kernel mode.\n"); > diff --git a/arch/powerpc/platforms/4xx/machine_check.c b/arch/powerpc/platforms/4xx/machine_check.c > index a71c29892a91..a905da1d6f41 100644 > --- a/arch/powerpc/platforms/4xx/machine_check.c > +++ b/arch/powerpc/platforms/4xx/machine_check.c > @@ -10,7 +10,7 @@ > > int machine_check_4xx(struct pt_regs *regs) > { > - unsigned long reason = regs->dsisr; > + unsigned long reason = regs->esr; > > if (reason & ESR_IMCP) { > printk("Instruction"); >