[PATCH] x86/microcode/intel: Quieten down microcode updates on large systems

[Andi Kleen]

From: Andi Kleen <a...@linux.intel.com>

On large systems the microcode driver is very noisy, because it prints
a line for each CPU. The lines are redundant because because usually
all CPUs are updated to the same microcode revision.

All other subsystems have been patched previously to not print
a line for each CPU. Only the microcode driver is left.

Only print an microcode revision update when something changed. This results
in typically only a single line being printed.

Signed-off-by: Andi Kleen <a...@linux.intel.com>
---
 arch/x86/kernel/cpu/microcode/intel.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c 
b/arch/x86/kernel/cpu/microcode/intel.c
index cbb3cf0..952c8a3 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -794,6 +794,7 @@ void reload_ucode_intel(void)
 
 static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 {
+       static struct cpu_signature prev;
        struct cpuinfo_x86 *c = &cpu_data(cpu_num);
        unsigned int val[2];
 
@@ -808,8 +809,14 @@ static int collect_cpu_info(int cpu_num, struct 
cpu_signature *csig)
        }
 
        csig->rev = c->microcode;
-       pr_info("CPU%d sig=0x%x, pf=0x%x, revision=0x%x\n",
-               cpu_num, csig->sig, csig->pf, csig->rev);
+
+       /* No extra locking on prev, races are harmless. */
+       if (csig->sig != prev.sig || csig->pf != prev.pf ||
+           csig->rev != prev.rev) {
+               pr_info("CPU sig=0x%x, pf=0x%x, revision=0x%x\n",
+                       csig->sig, csig->pf, csig->rev);
+               prev = *csig;
+       }
 
        return 0;
 }
@@ -838,6 +845,7 @@ static int apply_microcode_intel(int cpu)
        struct ucode_cpu_info *uci;
        struct cpuinfo_x86 *c;
        unsigned int val[2];
+       static int prev_rev;
 
        /* We should bind the task to the CPU */
        if (WARN_ON(raw_smp_processor_id() != cpu))
@@ -872,11 +880,14 @@ static int apply_microcode_intel(int cpu)
                return -1;
        }
 
-       pr_info("CPU%d updated to revision 0x%x, date = %04x-%02x-%02x\n",
-               cpu, val[1],
-               mc->hdr.date & 0xffff,
-               mc->hdr.date >> 24,
-               (mc->hdr.date >> 16) & 0xff);
+       if (val[1] != prev_rev) {
+               pr_info("CPU updated to revision 0x%x, date = %04x-%02x-%02x\n",
+                       val[1],
+                       mc->hdr.date & 0xffff,
+                       mc->hdr.date >> 24,
+                       (mc->hdr.date >> 16) & 0xff);
+               prev_rev = val[1];
+       }
 
        c = &cpu_data(cpu);
 
-- 
2.8.2