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Message-ID: <20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net> Date: Tue, 26 Dec 2017 23:43:54 -0600 From: Tom Lendacky <thomas.lendacky@....com> To: x86@...nel.org Cc: Dave Hansen <dave.hansen@...ux.intel.com>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Andy Lutomirski <luto@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de> 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 <thomas.lendacky@....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);
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