pve-edge-kernel/patches/kernel/0240-x86-cpu-x86-pti-Do-not-enable-PTI-on-AMD-processors.patch

From 5462db3d070845ecc34929b6f25a87efda023aae Mon Sep 17 00:00:00 2001
From: Tom Lendacky <[email protected]>
Date: Tue, 26 Dec 2017 23:43:54 -0600
Subject: [PATCH 240/241] x86/cpu, x86/pti: Do not enable PTI on AMD processors
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CVE-2017-5754

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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

(cherry picked from commit 694d99d40972f12e59a3696effee8a376b79d7c8)
Signed-off-by: Marcelo Henrique Cerri <[email protected]>
(cherry picked from commit 9d334f48f017b9c6457c6ba321e5a53a1cc6a5c7)
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 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 99f37d1636ff..1854dd8071a6 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);
 }
-- 
2.14.2