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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 6A074C4338F for ; Fri, 6 Aug 2021 06:53:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4820961167 for ; Fri, 6 Aug 2021 06:53:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243444AbhHFGxi (ORCPT ); Fri, 6 Aug 2021 02:53:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229635AbhHFGxh (ORCPT ); Fri, 6 Aug 2021 02:53:37 -0400 Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDAF2C061798 for ; Thu, 5 Aug 2021 23:53:21 -0700 (PDT) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4Ggx5B1S6Wz9sCD; Fri, 6 Aug 2021 16:53:17 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1628232798; bh=vD1LTdPK6JfRXO2TE9cg4Rh9PKZx4+TBHw0WLGKC9bU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=GVGwvFBGLVzVFjPmETJqgZJ/hNeJU5weXVURVKih5fKtMwzCjHMLjXuPm45N12vOp Vt6XopcGqXqlT3nEItSo7f5Y3vV5WTJz0POh+T0BOXc7y4DHJwUOBBuhwE+6UAaJWS MD/zjJc6lde91EIXiCeaIstPtyrr7kupmStC2oEzbiawq7S6UHRtOX/hbcphSmqTU3 hSAfl5ju8dTzc/ZoSiAR6ohFFZx+2CDnYOlhavYAwnY3R3A/oIYj5dAsPNpIIT4zgd ZYmfx++fkitquwKoVs1KVZYeQXU6OyMWznfHqJN4Ll2SkUbnPBygxyAtgwMom/v0pe Mz+ZGp9D9InZg== From: Michael Ellerman To: sxwjean@me.com, linuxppc-dev@lists.ozlabs.org Cc: oleg@redhat.com, benh@kernel.crashing.org, paulus@samba.org, ravi.bangoria@linux.ibm.com, christophe.leroy@csgroup.eu, 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 Subject: Re: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register In-Reply-To: <20210726143053.532839-1-sxwjean@me.com> References: <20210726143053.532839-1-sxwjean@me.com> Date: Fri, 06 Aug 2021 16:53:14 +1000 Message-ID: <874kc3njxh.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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. cheers