From e38319a2ac82701a3bc4b4686651a6f5c3f2b5fa Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Tue, 26 Dec 2017 23:43:54 -0600 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Dave Hansen Cc: Andy Lutomirski Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net --- 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 f2a94dfb434e9..b1be494ab4e8b 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); -- 2.39.5