From bd19a5e6b73df276e1ccedf9059e9ee70c372d7d Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 27 May 2009 21:56:55 +0200 Subject: [PATCH] x86, mce: check early in exception handler if panic is needed The exception handler should behave differently if the exception is fatal versus one that can be returned from. In the first case it should never clear any registers because these need to be preserved for logging after the next boot. Otherwise it should clear them on each CPU step by step so that other CPUs sharing the same bank don't see duplicate events. Otherwise we risk reporting events multiple times on any CPUs which have shared machine check banks, which is a common problem on Intel Nehalem which has both SMT (two CPU threads sharing banks) and shared machine check banks in the uncore. Determine early in a special pass if any event requires a panic. This uses the mce_severity() function added earlier. This is needed for the next patch. Also fixes a problem together with an earlier patch that corrected events weren't logged on a fatal MCE. [ Impact: Feature ] Signed-off-by: Andi Kleen Signed-off-by: Hidetoshi Seto Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mcheck/mce.c | 38 +++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 6773610061d8..5031814ac943 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -36,6 +36,7 @@ #include #include +#include "mce-internal.h" #include "mce.h" /* Handle unconfigured int18 (should never happen) */ @@ -191,7 +192,7 @@ static void print_mce(struct mce *m) "and contact your hardware vendor\n"); } -static void mce_panic(char *msg, struct mce *final) +static void mce_panic(char *msg, struct mce *final, char *exp) { int i; @@ -214,6 +215,8 @@ static void mce_panic(char *msg, struct mce *final) } if (final) print_mce(final); + if (exp) + printk(KERN_EMERG "Machine check: %s\n", exp); panic(msg); } @@ -357,6 +360,22 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b) } EXPORT_SYMBOL_GPL(machine_check_poll); +/* + * Do a quick check if any of the events requires a panic. + * This decides if we keep the events around or clear them. + */ +static int mce_no_way_out(struct mce *m, char **msg) +{ + int i; + + for (i = 0; i < banks; i++) { + m->status = mce_rdmsrl(MSR_IA32_MC0_STATUS + i*4); + if (mce_severity(m, tolerant, msg) >= MCE_PANIC_SEVERITY) + return 1; + } + return 0; +} + /* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. @@ -381,6 +400,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) */ int kill_it = 0; DECLARE_BITMAP(toclear, MAX_NR_BANKS); + char *msg = "Unknown"; atomic_inc(&mce_entry); @@ -395,10 +415,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) mce_setup(&m); m.mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); - - /* if the restart IP is not valid, we're done for */ - if (!(m.mcgstatus & MCG_STATUS_RIPV)) - no_way_out = 1; + no_way_out = mce_no_way_out(&m, &msg); barrier(); @@ -430,18 +447,13 @@ void do_machine_check(struct pt_regs *regs, long error_code) __set_bit(i, toclear); if (m.status & MCI_STATUS_EN) { - /* if PCC was set, there's no way out */ - no_way_out |= !!(m.status & MCI_STATUS_PCC); /* * If this error was uncorrectable and there was * an overflow, we're in trouble. If no overflow, * we might get away with just killing a task. */ - if (m.status & MCI_STATUS_UC) { - if (tolerant < 1 || m.status & MCI_STATUS_OVER) - no_way_out = 1; + if (m.status & MCI_STATUS_UC) kill_it = 1; - } } else { /* * Machine check event was not enabled. Clear, but @@ -483,7 +495,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) * has not set tolerant to an insane level, give up and die. */ if (no_way_out && tolerant < 3) - mce_panic("Machine check", &panicm); + mce_panic("Machine check", &panicm, msg); /* * If the error seems to be unrecoverable, something should be @@ -511,7 +523,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) if (user_space) { force_sig(SIGBUS, current); } else if (panic_on_oops || tolerant < 2) { - mce_panic("Uncorrected machine check", &panicm); + mce_panic("Uncorrected machine check", &panicm, msg); } } -- 2.39.2