Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966259AbbLPRXI (ORCPT ); Wed, 16 Dec 2015 12:23:08 -0500 Received: from mga04.intel.com ([192.55.52.120]:43165 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933033AbbLPRXG (ORCPT ); Wed, 16 Dec 2015 12:23:06 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,437,1444719600"; d="scan'208";a="842580036" Message-Id: In-Reply-To: References: From: Tony Luck Date: Tue, 15 Dec 2015 17:29:59 -0800 Subject: [PATCHV3 2/3] x86, ras: Extend machine check recovery code to annotated ring0 areas To: Ingo Molnar Cc: Borislav Petkov , Andrew Morton , Andy Lutomirski , Dan Williams , Elliott@vger.kernel.org, Robert (Persistent Memory) , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6478 Lines: 198 Extend the severity checking code to add a new context IN_KERN_RECOV which is used to indicate that the machine check was triggered by code in the kernel with a fixup entry. Add code to check for this situation and respond by altering the return IP to the fixup address. Major re-work to the tail code in do_machine_check() to make all this readable/maintainable. One functional change is that tolerant=3 no longer stops recovery actions. Revert to only skipping sending SIGBUS to the current process. Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/mcheck/mce-severity.c | 21 +++++++++- arch/x86/kernel/cpu/mcheck/mce.c | 70 ++++++++++++++++--------------- 2 files changed, 55 insertions(+), 36 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c index 9c682c222071..cc7136351820 100644 --- a/arch/x86/kernel/cpu/mcheck/mce-severity.c +++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c @@ -29,7 +29,7 @@ * panic situations) */ -enum context { IN_KERNEL = 1, IN_USER = 2 }; +enum context { IN_KERNEL = 1, IN_USER = 2, IN_KERNEL_RECOV = 3 }; enum ser { SER_REQUIRED = 1, NO_SER = 2 }; enum exception { EXCP_CONTEXT = 1, NO_EXCP = 2 }; @@ -48,6 +48,7 @@ static struct severity { #define MCESEV(s, m, c...) { .sev = MCE_ ## s ## _SEVERITY, .msg = m, ## c } #define KERNEL .context = IN_KERNEL #define USER .context = IN_USER +#define KERNEL_RECOV .context = IN_KERNEL_RECOV #define SER .ser = SER_REQUIRED #define NOSER .ser = NO_SER #define EXCP .excp = EXCP_CONTEXT @@ -87,6 +88,10 @@ static struct severity { EXCP, KERNEL, MCGMASK(MCG_STATUS_RIPV, 0) ), MCESEV( + PANIC, "In kernel and no restart IP", + EXCP, KERNEL_RECOV, MCGMASK(MCG_STATUS_RIPV, 0) + ), + MCESEV( DEFERRED, "Deferred error", NOSER, MASK(MCI_STATUS_UC|MCI_STATUS_DEFERRED|MCI_STATUS_POISON, MCI_STATUS_DEFERRED) ), @@ -123,6 +128,11 @@ static struct severity { MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, MCG_STATUS_RIPV) ), MCESEV( + AR, "Action required: data load in error recoverable area of kernel", + SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA), + KERNEL_RECOV + ), + MCESEV( AR, "Action required: data load error in a user process", SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA), USER @@ -170,6 +180,9 @@ static struct severity { ) /* always matches. keep at end */ }; +#define mc_recoverable(mcg) (((mcg) & (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) == \ + (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) + /* * If mcgstatus indicated that ip/cs on the stack were * no good, then "m->cs" will be zero and we will have @@ -183,7 +196,11 @@ static struct severity { */ static int error_context(struct mce *m) { - return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL; + if ((m->cs & 3) == 3) + return IN_USER; + if (mc_recoverable(m->mcgstatus) && search_mcexception_tables(m->ip)) + return IN_KERNEL_RECOV; + return IN_KERNEL; } /* diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 0111cd49ee94..e848b583e840 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -959,6 +959,20 @@ static void mce_clear_state(unsigned long *toclear) } } +static int do_memory_failure(struct mce *m) +{ + int flags = MF_ACTION_REQUIRED; + int ret; + + pr_err("Uncorrected hardware memory error in user-access at %llx", m->addr); + if (!(m->mcgstatus & MCG_STATUS_RIPV)) + flags |= MF_MUST_KILL; + ret = memory_failure(m->addr >> PAGE_SHIFT, MCE_VECTOR, flags); + if (ret) + pr_err("Memory error not recovered"); + return ret; +} + /* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. @@ -996,8 +1010,6 @@ void do_machine_check(struct pt_regs *regs, long error_code) DECLARE_BITMAP(toclear, MAX_NR_BANKS); DECLARE_BITMAP(valid_banks, MAX_NR_BANKS); char *msg = "Unknown"; - u64 recover_paddr = ~0ull; - int flags = MF_ACTION_REQUIRED; int lmce = 0; ist_enter(regs); @@ -1124,22 +1136,13 @@ void do_machine_check(struct pt_regs *regs, long error_code) } /* - * At insane "tolerant" levels we take no action. Otherwise - * we only die if we have no other choice. For less serious - * issues we try to recover, or limit damage to the current - * process. + * If tolerant is at an insane level we drop requests to kill + * processes and continue even when there is no way out. */ - if (cfg->tolerant < 3) { - if (no_way_out) - mce_panic("Fatal machine check on current CPU", &m, msg); - if (worst == MCE_AR_SEVERITY) { - recover_paddr = m.addr; - if (!(m.mcgstatus & MCG_STATUS_RIPV)) - flags |= MF_MUST_KILL; - } else if (kill_it) { - force_sig(SIGBUS, current); - } - } + if (cfg->tolerant == 3) + kill_it = 0; + else if (no_way_out) + mce_panic("Fatal machine check on current CPU", &m, msg); if (worst > 0) mce_report_event(regs); @@ -1147,25 +1150,24 @@ void do_machine_check(struct pt_regs *regs, long error_code) out: sync_core(); - if (recover_paddr == ~0ull) - goto done; + if (worst != MCE_AR_SEVERITY && !kill_it) + goto out_ist; - pr_err("Uncorrected hardware memory error in user-access at %llx", - recover_paddr); - /* - * We must call memory_failure() here even if the current process is - * doomed. We still need to mark the page as poisoned and alert any - * other users of the page. - */ - ist_begin_non_atomic(regs); - local_irq_enable(); - if (memory_failure(recover_paddr >> PAGE_SHIFT, MCE_VECTOR, flags) < 0) { - pr_err("Memory error not recovered"); - force_sig(SIGBUS, current); + /* Fault was in user mode and we need to take some action */ + if ((m.cs & 3) == 3) { + ist_begin_non_atomic(regs); + local_irq_enable(); + + if (kill_it || do_memory_failure(&m)) + force_sig(SIGBUS, current); + local_irq_disable(); + ist_end_non_atomic(); + } else { + if (!fixup_mcexception(regs)) + mce_panic("Failed kernel mode recovery", &m, NULL); } - local_irq_disable(); - ist_end_non_atomic(); -done: + +out_ist: ist_exit(regs); } EXPORT_SYMBOL_GPL(do_machine_check); -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/