From Tom Lendacky <> Subject [PATCH] x86/cpu, x86/pti: Do not enable PTI on AMD processors Date Tue, 26 Dec 2017 23:43:54 -0600 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>

---

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 c47de4e..7d9e3b0 100644

--- a/arch/x86/kernel/cpu/common.c

+++ b/arch/x86/kernel/cpu/common.c

@@ -923,8 +923,8 @@ 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);



