[PATCH 3.16 60/63] x86/cpu/AMD: Fix erratum 1076 (CPB bit)

[Ben Hutchings]

3.16.58-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp@xxxxxxx>

commit f7f3dc00f61261cdc9ccd8b886f21bc4dffd6fd9 upstream.

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@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sherry Hurwitz <sherry.hurwitz@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170907170821.16021-1-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16:
 - Change the added case into an if-statement
 - s/x86_stepping/x86_mask/]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/amd.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -533,6 +533,16 @@ static void init_amd_ln(struct cpuinfo_x
 	msr_set_bit(MSR_AMD64_DE_CFG, 31);
 }
 
+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)
 {
 	u32 dummy;
@@ -611,6 +621,9 @@ static void init_amd(struct cpuinfo_x86
 		clear_cpu_cap(c, X86_FEATURE_MCE);
 #endif
 
+	if (c->x86 == 0x17)
+		init_amd_zn(c);
+
 	/* Enable workaround for FXSAVE leak */
 	if (c->x86 >= 6)
 		set_cpu_cap(c, X86_FEATURE_FXSAVE_LEAK);