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From 51786b65797aed683ca72293a3cb86a2cab987c0 Mon Sep 17 00:00:00 2001
Message-Id: <51786b65797aed683ca72293a3cb86a2cab987c0.1514959852.git.jan.steffens@gmail.com>
In-Reply-To: <fb89d912d5f7289d3a922c77b671e36e1c740f5e.1514959852.git.jan.steffens@gmail.com>
References: <fb89d912d5f7289d3a922c77b671e36e1c740f5e.1514959852.git.jan.steffens@gmail.com>
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Tue, 26 Dec 2017 23:43:54 -0600
Subject: [PATCH 7/7] x86/cpu, x86/pti: Do not enable PTI on AMD processors
AMD processors are not subject to the types of attacks that the kernel
page table isolation feature protects against. The AMD microarchitecture
does not allow memory references, including speculative references, that
access higher privileged data when running in a lesser privileged mode
when that access would result in a page fault.
Disable page table isolation by default on AMD processors by not setting
the X86_BUG_CPU_INSECURE feature, which controls whether X86_FEATURE_PTI
is set.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/common.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f2a94dfb434e9a7c..b1be494ab4e8badf 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -899,8 +899,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
setup_force_cpu_cap(X86_FEATURE_ALWAYS);
- /* Assume for now that ALL x86 CPUs are insecure */
- setup_force_cpu_bug(X86_BUG_CPU_INSECURE);
+ if (c->x86_vendor != X86_VENDOR_AMD)
+ setup_force_cpu_bug(X86_BUG_CPU_INSECURE);
fpu__init_system(c);
--
2.15.1
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