From patchwork Fri Aug 16 08:04:11 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mahesh J Salgaonkar X-Patchwork-Id: 267568 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from ozlabs.org (localhost [IPv6:::1]) by ozlabs.org (Postfix) with ESMTP id 6B1552C039B for ; Fri, 16 Aug 2013 18:06:18 +1000 (EST) Received: by ozlabs.org (Postfix) id 943042C031D; Fri, 16 Aug 2013 18:04:17 +1000 (EST) Delivered-To: linuxppc-dev@ozlabs.org Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com [202.81.31.142]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp09.au.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 7EEAB2C0262 for ; Fri, 16 Aug 2013 18:04:17 +1000 (EST) Received: from /spool/local by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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To: linuxppc-dev , Benjamin Herrenschmidt From: Mahesh J Salgaonkar Date: Fri, 16 Aug 2013 13:34:11 +0530 Message-ID: <20130816080410.680.46919.stgit@mars.in.ibm.com> In-Reply-To: <20130816080213.680.50794.stgit@mars.in.ibm.com> References: <20130816080213.680.50794.stgit@mars.in.ibm.com> User-Agent: StGit/0.15-4-g042f-dirty MIME-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13081618-3568-0000-0000-00000417B52D Cc: Jeremy Kerr , Paul Mackerras , Anton Blanchard X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Mahesh Salgaonkar This patch introduces exclusive emergency stack for machine check exception. We use emergency stack to handle machine check exception so that we can save MCE information (srr1, srr0, dar and dsisr) before turning on ME bit and be ready for re-entrancy. This helps us to prevent clobbering of MCE information in case of nested machine checks. The reason for using emergency stack over normal kernel stack is that the machine check might occur in the middle of setting up a stack frame which may result into improper use of kernel stack. Signed-off-by: Mahesh Salgaonkar --- arch/powerpc/include/asm/paca.h | 9 +++++++++ arch/powerpc/kernel/setup_64.c | 8 +++++++- arch/powerpc/xmon/xmon.c | 2 ++ 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index 77c91e7..b4ca4e9 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -147,6 +147,15 @@ struct paca_struct { */ struct opal_machine_check_event *opal_mc_evt; #endif +#ifdef CONFIG_PPC_BOOK3S_64 + /* Exclusive emergency stack pointer for machine check exception. */ + void *mc_emergency_sp; + /* + * Flag to check whether we are in machine check early handler + * and already using emergency stack. + */ + u16 in_mce; +#endif /* Stuff for accurate time accounting */ u64 user_time; /* accumulated usermode TB ticks */ diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 389fb807..3fdbdb0 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -529,7 +529,8 @@ static void __init exc_lvl_early_init(void) /* * Stack space used when we detect a bad kernel stack pointer, and - * early in SMP boots before relocation is enabled. + * early in SMP boots before relocation is enabled. Exclusive emergency + * stack for machine checks. */ static void __init emergency_stack_init(void) { @@ -552,6 +553,11 @@ static void __init emergency_stack_init(void) sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); sp += THREAD_SIZE; paca[i].emergency_sp = __va(sp); + + /* emergency stack for machine check exception handling. */ + sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); + sp += THREAD_SIZE; + paca[i].mc_emergency_sp = __va(sp); } } diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index 96bf5bd..147a5e98 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -2044,6 +2044,8 @@ static void dump_one_paca(int cpu) DUMP(p, stab_addr, "lx"); #endif DUMP(p, emergency_sp, "p"); + DUMP(p, mc_emergency_sp, "p"); + DUMP(p, in_mce, "x"); DUMP(p, data_offset, "lx"); DUMP(p, hw_cpu_id, "x"); DUMP(p, cpu_start, "x");