perf/x86: Add a microcode revision check for SNB-PEBS

Recent Intel microcode resolved the SNB-PEBS issues, so conditionally
enable PEBS on SNB hardware depending on the microcode revision.

Thanks to Stephane for figuring out the various microcode revisions.

Suggested-by: Stephane Eranian <eranian@google.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-v3672ziwh9damwqwh1uz3krm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index 947e4c64b1d..1649cf899ad 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -87,6 +87,7 @@
 #include <asm/microcode.h>
 #include <asm/processor.h>
 #include <asm/cpu_device_id.h>
+#include <asm/perf_event.h>
 
 MODULE_DESCRIPTION("Microcode Update Driver");
 MODULE_AUTHOR("Tigran Aivazian <tigran@aivazian.fsnet.co.uk>");
@@ -277,7 +278,6 @@ static int reload_for_cpu(int cpu)
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	int err = 0;
 
-	mutex_lock(&microcode_mutex);
 	if (uci->valid) {
 		enum ucode_state ustate;
 
@@ -288,7 +288,6 @@ static int reload_for_cpu(int cpu)
 			if (ustate == UCODE_ERROR)
 				err = -EINVAL;
 	}
-	mutex_unlock(&microcode_mutex);
 
 	return err;
 }
@@ -309,6 +308,7 @@ static ssize_t reload_store(struct device *dev,
 		return size;
 
 	get_online_cpus();
+	mutex_lock(&microcode_mutex);
 	for_each_online_cpu(cpu) {
 		tmp_ret = reload_for_cpu(cpu);
 		if (tmp_ret != 0)
@@ -318,6 +318,9 @@ static ssize_t reload_store(struct device *dev,
 		if (!ret)
 			ret = tmp_ret;
 	}
+	if (!ret)
+		perf_check_microcode();
+	mutex_unlock(&microcode_mutex);
 	put_online_cpus();
 
 	if (!ret)
@@ -557,7 +560,8 @@ static int __init microcode_init(void)
 	mutex_lock(&microcode_mutex);
 
 	error = subsys_interface_register(&mc_cpu_interface);
-
+	if (!error)
+		perf_check_microcode();
 	mutex_unlock(&microcode_mutex);
 	put_online_cpus();