x86/mce: Prevent duplicate error records

A legitimate use case of the MCA infrastructure is to have the firmware
log all uncorrectable errors and also, have the OS see all correctable
errors.

The uncorrectable, UCNA errors are usually configured to be reported
through an SMI. CMCI, which is the correctable error reporting
interrupt, uses SMI too and having both enabled, leads to unnecessary
overhead.

So what ends up happening is, people disable CMCI in the wild and leave
on only the UCNA SMI.

When CMCI is disabled, the MCA infrastructure resorts to polling the MCA
banks. If a MCA MSR is shared between the logical threads, one error
ends up getting logged multiple times as the polling runs on every
logical thread.

Therefore, introduce locking on the Intel side of the polling routine to
prevent such duplicate error records from appearing.

Based on a patch by Aristeu Rozanski <aris@ruivo.org>.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Tony Luck <tony.luck@intel.com>
Acked-by: Aristeu Rozanski <aris@ruivo.org>
Link: https://lore.kernel.org/r/20230515143225.GC4090740@cathedrallabs.org

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 89e2aab5d34d8513208ec45313df25502c8713ad..b8ad5a5b4026965ddcaf06e2437ed582b986fde4 100644 (file)
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1608,6 +1608,13 @@ static void __start_timer(struct timer_list *t, unsigned long interval)
        local_irq_restore(flags);
 }
 
+static void mc_poll_banks_default(void)
+{
+       machine_check_poll(0, this_cpu_ptr(&mce_poll_banks));
+}
+
+void (*mc_poll_banks)(void) = mc_poll_banks_default;
+
 static void mce_timer_fn(struct timer_list *t)
 {
        struct timer_list *cpu_t = this_cpu_ptr(&mce_timer);
@@ -1618,7 +1625,7 @@ static void mce_timer_fn(struct timer_list *t)
        iv = __this_cpu_read(mce_next_interval);
 
        if (mce_available(this_cpu_ptr(&cpu_info))) {
-               machine_check_poll(0, this_cpu_ptr(&mce_poll_banks));
+               mc_poll_banks();
 
                if (mce_intel_cmci_poll()) {
                        iv = mce_adjust_timer(iv);

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index 95275a5e57e06ca292586a7cd4ff547b3eac69e1..f5323551c1a9a9aab0a87de057db19f6e1819b94 100644 (file)
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -56,6 +56,13 @@ static DEFINE_PER_CPU(int, cmci_backoff_cnt);
  */
 static DEFINE_RAW_SPINLOCK(cmci_discover_lock);
 
+/*
+ * On systems that do support CMCI but it's disabled, polling for MCEs can
+ * cause the same event to be reported multiple times because IA32_MCi_STATUS
+ * is shared by the same package.
+ */
+static DEFINE_SPINLOCK(cmci_poll_lock);
+
 #define CMCI_THRESHOLD         1
 #define CMCI_POLL_INTERVAL     (30 * HZ)
 #define CMCI_STORM_INTERVAL    (HZ)
@@ -426,12 +433,22 @@ void cmci_disable_bank(int bank)
        raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
 }
 
+/* Bank polling function when CMCI is disabled. */
+static void cmci_mc_poll_banks(void)
+{
+       spin_lock(&cmci_poll_lock);
+       machine_check_poll(0, this_cpu_ptr(&mce_poll_banks));
+       spin_unlock(&cmci_poll_lock);
+}
+
 void intel_init_cmci(void)
 {
        int banks;
 
-       if (!cmci_supported(&banks))
+       if (!cmci_supported(&banks)) {
+               mc_poll_banks = cmci_mc_poll_banks;
                return;
+       }
 
        mce_threshold_vector = intel_threshold_interrupt;
        cmci_discover(banks);

diff --git a/arch/x86/kernel/cpu/mce/internal.h b/arch/x86/kernel/cpu/mce/internal.h
index d2412ce2d312f4fc7771f8f276ac079e29371cd1..ed4a71c0f0938d159de0d76a8cb5510cb9d3a6d8 100644 (file)
--- a/arch/x86/kernel/cpu/mce/internal.h
+++ b/arch/x86/kernel/cpu/mce/internal.h
@@ -274,4 +274,5 @@ static __always_inline u32 mca_msr_reg(int bank, enum mca_msr reg)
        return 0;
 }
 
+extern void (*mc_poll_banks)(void);
 #endif /* __X86_MCE_INTERNAL_H__ */