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Message-ID: <20171228001931.GA15868@nazgul.tnic> Date: Thu, 28 Dec 2017 01:20:58 +0100 From: Borislav Petkov <bp@...en8.de> To: Tom Lendacky <thomas.lendacky@....com> Cc: x86@...nel.org, 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> Subject: Re: [PATCH] x86/cpu, x86/pti: Do not enable PTI on AMD processors On Tue, Dec 26, 2017 at 11:43:54PM -0600, Tom Lendacky wrote: > 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); Reviewed-by: Borislav Petkov <bp@...e.de> -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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