From a61fe491f34806939715879bb94a4c34ead44143 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 commit 694d99d40972f12e59a3696effee8a376b79d7c8 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 Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Dave Hansen Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- 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 b71dcb9675b3..75bdfa79bb24 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -768,8 +768,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) if (this_cpu->c_bsp_init) this_cpu->c_bsp_init(c); - /* 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); } void __init early_cpu_init(void) -- 2.30.2