From 9ec2b3153415ca412de6471baec2e61ec89997e1 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 15 Jan 2014 00:07:11 +0100 Subject: [PATCH] x86, cpu, amd: Add workaround for family 16h, erratum 793 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 Link: http://lkml.kernel.org/r/20140114230711.GS29865@pd.tnic Tested-by: Aravind Gopalakrishnan Signed-off-by: H. Peter Anvin [bwh: Backported to 3.2: - Adjust filename - Venkatesh Srinivas pointed out we should use {rd,wr}msrl_safe() to avoid crashing on KVM. This was fixed upstream by commit 8f86a7373a1c ("x86, AMD: Convert to the new bit access MSR accessors") but that's too much trouble to backport. Here we must use {rd,wr}msrl_amd_safe().] Signed-off-by: Ben Hutchings Cc: Moritz Muehlenhoff Cc: Venkatesh Srinivas --- arch/x86/include/asm/msr-index.h | 1 + arch/x86/kernel/cpu/amd.c | 10 ++++++++++ 2 files changed, 11 insertions(+) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index a6962d9161a0..5538b138b3df 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -123,6 +123,7 @@ #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_IBSFETCHCTL 0xc0011030 #define MSR_AMD64_IBSFETCHLINAD 0xc0011031 diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 2d44a28be0ea..60d4c3351cdb 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -408,6 +408,16 @@ static void __cpuinit early_init_amd_mc(struct cpuinfo_x86 *c) c->x86_coreid_bits = bits; #endif + + /* F16h erratum 793, CVE-2013-6885 */ + if (c->x86 == 0x16 && c->x86_model <= 0xf) { + u64 val; + + if (!rdmsrl_amd_safe(MSR_AMD64_LS_CFG, &val) && + !(val & BIT(15))) + wrmsrl_amd_safe(MSR_AMD64_LS_CFG, val | BIT(15)); + } + } static void __cpuinit bsp_init_amd(struct cpuinfo_x86 *c) -- 2.39.2