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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 73C5BC4338F for ; Fri, 6 Aug 2021 13:14:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 509F860EEA for ; Fri, 6 Aug 2021 13:14:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343999AbhHFNPF (ORCPT ); Fri, 6 Aug 2021 09:15:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343992AbhHFNPE (ORCPT ); Fri, 6 Aug 2021 09:15:04 -0400 Received: from mail-lj1-x236.google.com (mail-lj1-x236.google.com [IPv6:2a00:1450:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFF73C061798 for ; Fri, 6 Aug 2021 06:14:48 -0700 (PDT) Received: by mail-lj1-x236.google.com with SMTP id m18so584722ljo.1 for ; Fri, 06 Aug 2021 06:14:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=D1EUQQB8pNWqOdaIHcqaccRGVpN7D96fkqmkWU/G1Go=; b=VBFkSeoM0MDEuRDVWRNzCSd8lUuAkAkwl8MOor8uD1xzJOeuHOGG08wna9pkbp49/B kDK7sKNj69dWKTUQ1tmJN7nnHP7YAQvMvs0YP7azUuJolNS1P3ABKJx1rzpQhRyGcthi 2wIqpDEUbZ2zNHVCSSFq2sHeCk1/i8K7rYHGo7bZfjBV1j1CKO7oJifr64i5oO4CaU8h bLkx5hPffsukaI6cOqj4Qk2Yme7UWPP1uuEnyyK48RPXh/3PhhpMeGSsF25zVQKTvFi3 vkDPR0yn3nGdaOmjpGmxQNAsKqRySw4QwWGiAbetv4ZQrM8vi2mzJZj0Ah/14Ml0yy/A 2TZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=D1EUQQB8pNWqOdaIHcqaccRGVpN7D96fkqmkWU/G1Go=; b=VneJre2ykRN+3sjqVWKTjikngjIVK//1P+VvbGlUX4feS0pzpQDDZVwwG5xmnX15zL /z39ktN2evtHgdcj25C9tkWPTrgWhEPuUBAwfvLrOjXgwY9onSdpW8YAfTrwKQEOyezV fTRSEHgHJyjefFr44PlsWWZo92qrrcsV02RoDCfDijju5fNjacoZOpshWIVPtI00MhfA bYgvZQkShb0MWB4WAl9xYTPP51nA87lYYHWibZ2/2WPFeZoh5occ8JuRIpPiNjXKpdeX qT07YPzOOUebwQnu7m9PhUiF7NbwD3MHCm4r+J0fZb2wM/8Y1a4JcJxba0PIRTMGaCKr Iezw== X-Gm-Message-State: AOAM531INoSF32Wcs1HMxbahzjDiqPVssWML2bDFoNgIpj7JOGRRmzYe z2hSxdLfGtRcFrxK1CV+KPgg2kxtahQ4/kW/+MQ= X-Google-Smtp-Source: ABdhPJw1QTWFG3ah81HEQQrWVxzoREAZSPfao1dbNbVueBqoKQY3vEIVZFTsb4casd/1Och6p5hRNeRES+NFUuKDztA= X-Received: by 2002:a2e:9d47:: with SMTP id y7mr6390517ljj.408.1628255687307; Fri, 06 Aug 2021 06:14:47 -0700 (PDT) MIME-Version: 1.0 References: <20210726143053.532839-1-sxwjean@me.com> <874kc3njxh.fsf@mpe.ellerman.id.au> In-Reply-To: <874kc3njxh.fsf@mpe.ellerman.id.au> From: Xiongwei Song Date: Fri, 6 Aug 2021 21:14:21 +0800 Message-ID: Subject: Re: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register To: Michael Ellerman Cc: Xiongwei Song , PowerPC , oleg@redhat.com, Benjamin Herrenschmidt , Paul Mackerras , ravi.bangoria@linux.ibm.com, Christophe Leroy , npiggin@gmail.com, aneesh.kumar@linux.ibm.com, sandipan@linux.ibm.com, efremov@linux.com, peterx@redhat.com, akpm@linux-foundation.org, Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 6, 2021 at 2:53 PM Michael Ellerman wrote: > > sxwjean@me.com writes: > > 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. > > > > 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; > > + }; > > I don't mind doing that. > > > 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 */ > > }; > > But I'm not sure about the use of anonymous unions in UAPI headers. Old > compilers don't support them, so there's a risk of breakage. > > I'd rather we didn't touch the uapi version. Ok. Will discard the change. > > > > 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); > > As Christophe said, I don't thinks this is an improvement. > > It makes the code less readable. If anyone is confused about what is > passed to ___do_page_fault() they can either read the comment above it, > or look at the definition of pt_regs to see that esr and dsisr share > storage. Ok, thanks a lot. Will send v2. Regards, Xiongwei > > cheers