[PATCH v3] x86/microcode/intel: Blacklist the specific BDW-EP for late loading

[Jia Zhang]

Instead of blacklisting all Broadwell processorsi for running a late
loading, only BDW-EP (signature 406f1) with the microcode version
less than 0x0b000021 needs to be blacklisted.

This is documented in the the public documentation #334165 (See the
item BDF90 for details).

Signed-off-by: Jia Zhang <qianyue.zj@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/intel.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 8ccdca6..d2c1638 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -910,8 +910,15 @@ static bool is_blacklisted(unsigned int cpu)
 {
 	struct cpuinfo_x86 *c = &cpu_data(cpu);
 
-	if (c->x86 == 6 && c->x86_model == INTEL_FAM6_BROADWELL_X) {
-		pr_err_once("late loading on model 79 is disabled.\n");
+	/*
+	 * The Broadwell-EP processor with the microcode version less
+	 * then 0x0b000021 may reault in system hang when running a late
+	 * loading. This behavior is documented in item BDF90, #334165
+	 * (Intel Xeon Processor E7-8800/4800 v4 Product Family).
+	 */
+	if (c->x86 == 6 && c->x86_model == INTEL_FAM6_BROADWELL_X &&
+	    c->x86_mask == 0x01 && c->microcode < 0x0b000021U) {
+		pr_err_once("late loading on model 79 (sig 64f1) is disabled.\n");
 		return true;
 	}
 
-- 
1.8.3.1