x86/cpu/AMD: Fix erratum 1076 (CPB bit)

CPUID Fn8000_0007_EDX[CPB] is wrongly 0 on models up to B1. But they do
support CPB (AMD's Core Performance Boosting cpufreq CPU feature), so fix that.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sherry Hurwitz <sherry.hurwitz@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170907170821.16021-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 9862e2cd6d93..d58184b7cd44 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -763,6 +763,16 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
         }
 }
 
+static void init_amd_zn(struct cpuinfo_x86 *c)
+{
+        /*
+         * Fix erratum 1076: CPB feature bit not being set in CPUID. It affects
+         * all up to and including B1.
+         */
+        if (c->x86_model <= 1 && c->x86_mask <= 1)
+                set_cpu_cap(c, X86_FEATURE_CPB);
+}
+
 static void init_amd(struct cpuinfo_x86 *c)
 {
         early_init_amd(c);
@@ -791,6 +801,7 @@ static void init_amd(struct cpuinfo_x86 *c)
         case 0x10: init_amd_gh(c); break;
         case 0x12: init_amd_ln(c); break;
         case 0x15: init_amd_bd(c); break;
+        case 0x17: init_amd_zn(c); break;
         }
 
         /* Enable workaround for FXSAVE leak */