From ea431643d6c38728195e2c456801c3ef66bb9991 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Thu, 17 Apr 2014 10:25:53 +0200 Subject: x86/mce: Fix CMCI preemption bugs The following commit: 27f6c573e0f7 ("x86, CMCI: Add proper detection of end of CMCI storms") Added two preemption bugs: - machine_check_poll() does a get_cpu_var() without a matching put_cpu_var(), which causes preemption imbalance and crashes upon bootup. - it does percpu ops without disabling preemption. Preemption is not disabled due to the mistaken use of a raw spinlock. To fix these bugs fix the imbalance and change cmci_discover_lock to a regular spinlock. Reported-by: Owen Kibel Reported-by: Linus Torvalds Signed-off-by: Ingo Molnar Cc: Chen, Gong Cc: Josh Boyer Cc: Tony Luck Cc: Peter Zijlstra Cc: Alexander Todorov Cc: Borislav Petkov Link: http://lkml.kernel.org/n/tip-jtjptvgigpfkpvtQxpEk1at2@git.kernel.org Signed-off-by: Ingo Molnar -- arch/x86/kernel/cpu/mcheck/mce.c | 4 +--- arch/x86/kernel/cpu/mcheck/mce_intel.c | 18 +++++++++--------- 2 files changed, 10 insertions(+), 12 deletions(-) --- arch/x86/kernel/cpu/mcheck/mce.c | 4 +--- arch/x86/kernel/cpu/mcheck/mce_intel.c | 18 +++++++++--------- 2 files changed, 10 insertions(+), 12 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index eeee23ff75ef..68317c80de7f 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -598,7 +598,6 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b) { struct mce m; int i; - unsigned long *v; this_cpu_inc(mce_poll_count); @@ -618,8 +617,7 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b) if (!(m.status & MCI_STATUS_VAL)) continue; - v = &get_cpu_var(mce_polled_error); - set_bit(0, v); + this_cpu_write(mce_polled_error, 1); /* * Uncorrected or signalled events are handled by the exception * handler when it is enabled, so don't process those here. diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c index 3bdb95ae8c43..9a316b21df8b 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_intel.c +++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c @@ -42,7 +42,7 @@ static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned); * cmci_discover_lock protects against parallel discovery attempts * which could race against each other. */ -static DEFINE_RAW_SPINLOCK(cmci_discover_lock); +static DEFINE_SPINLOCK(cmci_discover_lock); #define CMCI_THRESHOLD 1 #define CMCI_POLL_INTERVAL (30 * HZ) @@ -144,14 +144,14 @@ static void cmci_storm_disable_banks(void) int bank; u64 val; - raw_spin_lock_irqsave(&cmci_discover_lock, flags); + spin_lock_irqsave(&cmci_discover_lock, flags); owned = __get_cpu_var(mce_banks_owned); for_each_set_bit(bank, owned, MAX_NR_BANKS) { rdmsrl(MSR_IA32_MCx_CTL2(bank), val); val &= ~MCI_CTL2_CMCI_EN; wrmsrl(MSR_IA32_MCx_CTL2(bank), val); } - raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); + spin_unlock_irqrestore(&cmci_discover_lock, flags); } static bool cmci_storm_detect(void) @@ -211,7 +211,7 @@ static void cmci_discover(int banks) int i; int bios_wrong_thresh = 0; - raw_spin_lock_irqsave(&cmci_discover_lock, flags); + spin_lock_irqsave(&cmci_discover_lock, flags); for (i = 0; i < banks; i++) { u64 val; int bios_zero_thresh = 0; @@ -266,7 +266,7 @@ static void cmci_discover(int banks) WARN_ON(!test_bit(i, __get_cpu_var(mce_poll_banks))); } } - raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); + spin_unlock_irqrestore(&cmci_discover_lock, flags); if (mca_cfg.bios_cmci_threshold && bios_wrong_thresh) { pr_info_once( "bios_cmci_threshold: Some banks do not have valid thresholds set\n"); @@ -316,10 +316,10 @@ void cmci_clear(void) if (!cmci_supported(&banks)) return; - raw_spin_lock_irqsave(&cmci_discover_lock, flags); + spin_lock_irqsave(&cmci_discover_lock, flags); for (i = 0; i < banks; i++) __cmci_disable_bank(i); - raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); + spin_unlock_irqrestore(&cmci_discover_lock, flags); } static void cmci_rediscover_work_func(void *arg) @@ -360,9 +360,9 @@ void cmci_disable_bank(int bank) if (!cmci_supported(&banks)) return; - raw_spin_lock_irqsave(&cmci_discover_lock, flags); + spin_lock_irqsave(&cmci_discover_lock, flags); __cmci_disable_bank(bank); - raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); + spin_unlock_irqrestore(&cmci_discover_lock, flags); } static void intel_init_cmci(void) -- cgit v1.2.1