linux-kernel - Re: [PATCH PATCH 9/9] x86/rfds: Exclude P-only parts from the RFDS affected list

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Date: Mon, 17 Jun 2024 07:34:22 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Andrew Cooper <andrew.cooper3@...rix.com>,
 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org
Cc: daniel.sneddon@...ux.intel.com, tony.luck@...el.com,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Josh Poimboeuf <jpoimboe@...nel.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH PATCH 9/9] x86/rfds: Exclude P-only parts from the RFDS
 affected list

On 6/17/24 02:43, Andrew Cooper wrote:
> On 17/06/2024 10:12 am, Pawan Gupta wrote:
>> +	VULNBL_INTEL_CPU_TYPE (RAPTORLAKE,	X86_CPU_TYPE_INTEL_ATOM,	RFDS),
>> +	VULNBL_INTEL_CPU_TYPE (ALDERLAKE,	X86_CPU_TYPE_INTEL_ATOM,	RFDS),
> 
> How does this work?
> 
> Being __initconst, this is only evaluated on the BSP.
> 
> P-only and mixed P/E systems won't see X86_CPU_TYPE_INTEL_ATOM, even if
> there are ATOM APs to bring up later.

The X86_CPU_TYPE_* is only used on the boot CPU on non-hybrids.  Hybrids
(independent of the boot CPU type) should be considered vulnerable no
matter what.