From 54467353a96577f840cd2348981417c559b21b4b Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Thu, 10 Nov 2016 14:10:53 +0100 Subject: [PATCH] x86/MCE: Correct TSC timestamping of error records We did have logic in the MCE code which would TSC-timestamp an error record only when it is exact - i.e., when it wasn't detected by polling. This isn't the case anymore. So let's fix that: We have a valid TSC timestamp in the error record only when it has been a precise detection, i.e., either in the #MC handler or in one of the interrupt handlers (thresholding, deferred, ...). All other error records still have mce.time which contains the wall time in order to be able to place the error record in time at least approximately. Also, this fixes another bug where machine_check_poll() would clear mce.tsc unconditionally even if we requested precise MCP_TIMESTAMP logging. The proper fix would be to generate timestamp only when it has been requested and not always. But that would require a more thorough code audit of all mce_gather_info/mce_setup() users. Add a FIXME for now. Signed-off-by: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Cc: Tony Luck Cc: kernel test robot Cc: linux-edac Cc: lkp@01.org Link: http://lkml.kernel.org/r/20161110131053.kybsijfs5venpjnf@pd.tnic Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/mcheck/mce.c | 16 ++++++++++------ arch/x86/kernel/cpu/mcheck/mce_intel.c | 4 ++-- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 4ca00474804b..aab96f8d52b0 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -706,6 +706,15 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b) mce_gather_info(&m, NULL); + /* + * m.tsc was set in mce_setup(). Clear it if not requested. + * + * FIXME: Propagate @flags to mce_gather_info/mce_setup() to avoid + * that dance. + */ + if (!(flags & MCP_TIMESTAMP)) + m.tsc = 0; + for (i = 0; i < mca_cfg.banks; i++) { if (!mce_banks[i].ctl || !test_bit(i, *b)) continue; @@ -713,14 +722,12 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b) m.misc = 0; m.addr = 0; m.bank = i; - m.tsc = 0; barrier(); m.status = mce_rdmsrl(msr_ops.status(i)); if (!(m.status & MCI_STATUS_VAL)) continue; - /* * Uncorrected or signalled events are handled by the exception * handler when it is enabled, so don't process those here. @@ -735,9 +742,6 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b) mce_read_aux(&m, i); - if (!(flags & MCP_TIMESTAMP)) - m.tsc = 0; - severity = mce_severity(&m, mca_cfg.tolerant, NULL, false); if (severity == MCE_DEFERRED_SEVERITY && memory_error(&m)) @@ -1394,7 +1398,7 @@ static void mce_timer_fn(unsigned long data) iv = __this_cpu_read(mce_next_interval); if (mce_available(this_cpu_ptr(&cpu_info))) { - machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_poll_banks)); + machine_check_poll(0, this_cpu_ptr(&mce_poll_banks)); if (mce_intel_cmci_poll()) { iv = mce_adjust_timer(iv); diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c index 1defb8ea882c..be0b2fad47c5 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_intel.c +++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c @@ -130,7 +130,7 @@ bool mce_intel_cmci_poll(void) * Reset the counter if we've logged an error in the last poll * during the storm. */ - if (machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned))) + if (machine_check_poll(0, this_cpu_ptr(&mce_banks_owned))) this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL); else this_cpu_dec(cmci_backoff_cnt); @@ -342,7 +342,7 @@ void cmci_recheck(void) return; local_irq_save(flags); - machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned)); + machine_check_poll(0, this_cpu_ptr(&mce_banks_owned)); local_irq_restore(flags); } -- 2.20.1