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

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Message-ID: <d7c70d92-4d19-4c1e-81c9-d4c0cd34eda8@citrix.com>
Date: Mon, 17 Jun 2024 10:43:07 +0100
From: Andrew Cooper <andrew.cooper3@...rix.com>
To: 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 17/06/2024 10:12 am, Pawan Gupta wrote:
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 7e3b09b0f82c..73ec66321758 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1209,6 +1209,9 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
>  #define VULNBL_INTEL_STEPPINGS(vfm, steppings, issues)	\
>  	X86_MATCH_VFM_STEPPINGS(INTEL_##vfm, steppings, issues)
>  
> +#define VULNBL_INTEL_CPU_TYPE(vfm, cpu_type, issues)	\
> +	X86_MATCH_VFM_CPU_TYPE(INTEL_##vfm, cpu_type, issues)
> +
>  #define VULNBL_AMD(family, blacklist)		\
>  	VULNBL(AMD, family, X86_MODEL_ANY, blacklist)
>  
> @@ -1255,9 +1258,7 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
>  	VULNBL_INTEL(TIGERLAKE,		GDS),
>  	VULNBL_INTEL(LAKEFIELD,		MMIO | MMIO_SBDS | RETBLEED),
>  	VULNBL_INTEL(ROCKETLAKE,	MMIO | RETBLEED | GDS),
> -	VULNBL_INTEL(ALDERLAKE,		RFDS),
>  	VULNBL_INTEL(ALDERLAKE_L,	RFDS),
> -	VULNBL_INTEL(RAPTORLAKE,	RFDS),
>  	VULNBL_INTEL(RAPTORLAKE_P,	RFDS),
>  	VULNBL_INTEL(RAPTORLAKE_S,	RFDS),
>  	VULNBL_INTEL(ATOM_GRACEMONT,	RFDS),
> @@ -1271,6 +1272,8 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
>  	/* Match more than Vendor/Family/Model */
>  	VULNBL_INTEL_STEPPINGS(COMETLAKE_L,	X86_STEPPINGS(0x0, 0x0),	MMIO | RETBLEED),
>  	VULNBL_INTEL	      (COMETLAKE_L,					MMIO | MMIO_SBDS | RETBLEED | GDS),
> +	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.

~Andrew