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Message-ID: <26b626e4-d01b-4a43-1c70-a4db7322dbbe@amd.com> Date: Wed, 27 Dec 2017 08:47:18 -0600 From: Tom Lendacky <thomas.lendacky@....com> To: Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org Cc: 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: Re: [PATCH] x86/cpu, x86/pti: Do not enable PTI on AMD processors On 12/27/2017 2:48 AM, Dave Hansen wrote: > On 12/26/2017 09:43 PM, Tom Lendacky wrote: >> --- 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); > > Does this disable it in a way that it can be turned back on via the > kernel command-line? > Yes, specifying pti=on on the command line will turn kernel page table isolation on regardless of this setting. Thanks, Tom > This is a rather wide class of issues and I would rather not just > hard-code it in a way that we say one vendor has never and will never be > affected. >
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