--- /dev/null
+From 3b56496865f9f7d9bcb2f93b44c63f274f08e3b6 Mon Sep 17 00:00:00 2001
+From: Borislav Petkov <bp@suse.de>
+Date: Wed, 15 Jan 2014 00:07:11 +0100
+Subject: x86, cpu, amd: Add workaround for family 16h, erratum 793
+
+From: Borislav Petkov <bp@suse.de>
+
+commit 3b56496865f9f7d9bcb2f93b44c63f274f08e3b6 upstream.
+
+This adds the workaround for erratum 793 as a precaution in case not
+every BIOS implements it. This addresses CVE-2013-6885.
+
+Erratum text:
+
+[Revision Guide for AMD Family 16h Models 00h-0Fh Processors,
+document 51810 Rev. 3.04 November 2013]
+
+793 Specific Combination of Writes to Write Combined Memory Types and
+Locked Instructions May Cause Core Hang
+
+Description
+
+Under a highly specific and detailed set of internal timing
+conditions, a locked instruction may trigger a timing sequence whereby
+the write to a write combined memory type is not flushed, causing the
+locked instruction to stall indefinitely.
+
+Potential Effect on System
+
+Processor core hang.
+
+Suggested Workaround
+
+BIOS should set MSR
+C001_1020[15] = 1b.
+
+Fix Planned
+
+No fix planned
+
+[ hpa: updated description, fixed typo in MSR name ]
+
+Signed-off-by: Borislav Petkov <bp@suse.de>
+Link: http://lkml.kernel.org/r/20140114230711.GS29865@pd.tnic
+Tested-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
+Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/x86/include/uapi/asm/msr-index.h | 1 +
+ arch/x86/kernel/cpu/amd.c | 10 ++++++++++
+ 2 files changed, 11 insertions(+)
+
+--- a/arch/x86/include/uapi/asm/msr-index.h
++++ b/arch/x86/include/uapi/asm/msr-index.h
+@@ -184,6 +184,7 @@
+ #define MSR_AMD64_PATCH_LOADER 0xc0010020
+ #define MSR_AMD64_OSVW_ID_LENGTH 0xc0010140
+ #define MSR_AMD64_OSVW_STATUS 0xc0010141
++#define MSR_AMD64_LS_CFG 0xc0011020
+ #define MSR_AMD64_DC_CFG 0xc0011022
+ #define MSR_AMD64_BU_CFG2 0xc001102a
+ #define MSR_AMD64_IBSFETCHCTL 0xc0011030
+--- a/arch/x86/kernel/cpu/amd.c
++++ b/arch/x86/kernel/cpu/amd.c
+@@ -508,6 +508,16 @@ static void early_init_amd(struct cpuinf
+ set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
+ }
+ #endif
++
++ /* F16h erratum 793, CVE-2013-6885 */
++ if (c->x86 == 0x16 && c->x86_model <= 0xf) {
++ u64 val;
++
++ rdmsrl(MSR_AMD64_LS_CFG, val);
++ if (!(val & BIT(15)))
++ wrmsrl(MSR_AMD64_LS_CFG, val | BIT(15));
++ }
++
+ }
+
+ static const int amd_erratum_383[];