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Subject[PATCH 3.16 245/346] x86/AMD: Apply erratum 665 on machines without a BIOS fix
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Emanuel Czirai <icanrealizeum@gmail.com>

commit d1992996753132e2dafe955cccb2fb0714d3cfc4 upstream.

AMD F12h machines have an erratum which can cause DIV/IDIV to behave
unpredictably. The workaround is to set MSRC001_1029[31] but sometimes
there is no BIOS update containing that workaround so let's do it
ourselves unconditionally. It is simple enough.

[ Borislav: Wrote commit message. ]

Signed-off-by: Emanuel Czirai <icanrealizeum@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Yaowu Xu <yaowu@google.com>
Link: http://lkml.kernel.org/r/20160902053550.18097-1-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bwh: Backported to 3.16:
- Add an if-statement to init_amd() in place of the switch
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -522,6 +522,17 @@ static const int amd_erratum_383[];
static const int amd_erratum_400[];
static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum);

+#define MSR_AMD64_DE_CFG 0xC0011029
+
+static void init_amd_ln(struct cpuinfo_x86 *c)
+{
+ /*
+ * Apply erratum 665 fix unconditionally so machines without a BIOS
+ * fix work.
+ */
+ msr_set_bit(MSR_AMD64_DE_CFG, 31);
+}
+
static void init_amd(struct cpuinfo_x86 *c)
{
u32 dummy;
@@ -614,6 +625,9 @@ static void init_amd(struct cpuinfo_x86
}
}

+ if (c->x86 == 0x12)
+ init_amd_ln(c);
+
/* re-enable TopologyExtensions if switched off by BIOS */
if ((c->x86 == 0x15) &&
(c->x86_model >= 0x10) && (c->x86_model <= 0x1f) &&
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