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x86/cpu, x86/pti: Do not enable PTI on AMD processors

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commit 694d99d409 upstream.

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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net
Cc: Nick Lowe <nick.lowe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tom Lendacky
2017-12-26 23:43:54 -06:00
committed by Greg Kroah-Hartman
parent 5ecd5c8388
commit 6b1c99e275
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/cpu/common.c
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@@ -831,8 +831,8 @@ 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_MELTDOWN);
if (c->x86_vendor != X86_VENDOR_AMD)
setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN);
setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
setup_force_cpu_bug(X86_BUG_SPECTRE_V2);