[PATCH] x86, CPU, AMD: Add workaround for family 16h, erratum 793

[Borislav Petkov]

From: Borislav Petkov <bp@xxxxxxx>

This adds the workaround for erratum 793 as a precaution in case not
every BIOS implements it. This addresses CVE-2013-6885.

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/amd.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 4a48e8bbd857..e4d6f8c91f51 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -507,6 +507,17 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 			set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
 	}
 #endif
+
+#define MSR_AMD_LS_CFG	0xc0011020
+	/* F16h, models 00h-0fh, erratum 793 */
+	if (c->x86 == 0x16 && c->x86_model <= 0xf) {
+		u64 val;
+
+		rdmsrl(MSR_AMD_LS_CFG, val);
+		if (!(val & BIT(15)))
+			wrmsrl(MSR_AMD_LS_CFG, val | BIT(15));
+	}
+
 }
 
 static const int amd_erratum_383[];
-- 
1.8.5.2.192.g7794a68

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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