[PATCH 4.4 086/107] x86/cpu/AMD: Fix erratum 1076 (CPB bit)

From: Greg Kroah-Hartman
Date: Mon Jul 23 2018 - 08:47:02 EST


4.4-stable 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>
Signed-off-by: Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@xxxxxxxxx>
Reviewed-by: Alexey Makhalov <amakhalov@xxxxxxxxxx>
Reviewed-by: Bo Gan <ganb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---

arch/x86/kernel/cpu/amd.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -713,6 +713,16 @@ static void init_amd_bd(struct cpuinfo_x
}
}

+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;
@@ -743,6 +753,7 @@ static void init_amd(struct cpuinfo_x86
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 */