[PATCH 2/6] x86-mce: Modify CMCI storm exit to reenable instead of rediscover banks.

[Havard Skinnemoen <hskinnemoen@google.com>]

From: Ewout van Bekkum <ewout@google.com>

The CMCI storm handler previously called cmci_reenable() when exiting a
CMCI storm. However, when entering a CMCI storm the bank ownership was
not relinquished by the affected CPUs. The CMCIs were only disabled via
cmci_storm_disable_banks(). The handler was updated to instead call a
new function, cmci_storm_enable_banks(), to reenable CMCI on the already
owned banks instead of rediscovering CMCI banks (which were still owned
but disabled).

Signed-off-by: Ewout van Bekkum <ewout@google.com>
Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
---
 arch/x86/kernel/cpu/mcheck/mce_intel.c | 50 ++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 26eb8d3..d015daf 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -104,6 +104,38 @@ void mce_intel_hcpu_update(unsigned long cpu)
 	per_cpu(cmci_storm_state, cpu) = CMCI_STORM_NONE;
 }
 
+static void cmci_storm_disable_banks(void)
+{
+	unsigned long flags, *owned;
+	int bank;
+	u64 val;
+
+	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);
+	}
+	spin_unlock_irqrestore(&cmci_discover_lock, flags);
+}
+
+static void cmci_storm_enable_banks(void)
+{
+	unsigned long flags, *owned;
+	int bank;
+	u64 val;
+
+	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);
+	}
+	spin_unlock_irqrestore(&cmci_discover_lock, flags);
+}
+
 unsigned long mce_intel_adjust_timer(unsigned long interval)
 {
 	int r;
@@ -132,7 +164,7 @@ unsigned long mce_intel_adjust_timer(unsigned long interval)
 		 */
 		if (!atomic_read(&cmci_storm_on_cpus)) {
 			__this_cpu_write(cmci_storm_state, CMCI_STORM_NONE);
-			cmci_reenable();
+			cmci_storm_enable_banks();
 			cmci_recheck();
 		}
 		return cmci_poll_interval();
@@ -145,22 +177,6 @@ unsigned long mce_intel_adjust_timer(unsigned long interval)
 	}
 }
 
-static void cmci_storm_disable_banks(void)
-{
-	unsigned long flags, *owned;
-	int bank;
-	u64 val;
-
-	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);
-	}
-	spin_unlock_irqrestore(&cmci_discover_lock, flags);
-}
-
 static bool cmci_storm_detect(void)
 {
 	unsigned int cnt = __this_cpu_read(cmci_storm_cnt);
-- 
2.0.0.526.g5318336