linux-kernel - [PATCH v6 5/5] x86/rfds: Exclude P-only parts from the RFDS affected list

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Message-ID: <20250305-add-cpu-type-v6-5-4741735bcd75@linux.intel.com>
Date: Wed, 5 Mar 2025 23:13:52 -0800
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: 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>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Brice Goglin <brice.goglin@...il.com>,
	Mario Limonciello <mario.limonciello@....com>,
	Perry Yuan <Perry.Yuan@....com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH v6 5/5] x86/rfds: Exclude P-only parts from the RFDS affected
 list

The affected CPU table (cpu_vuln_blacklist) marks Alderlake and Raptorlake
P-only parts affected by RFDS. This is not true because only E-cores are
affected by RFDS. With the current family/model matching it is not possible
to differentiate the unaffected parts, as the affected and unaffected
hybrid variants have the same model number.

Add a cpu-type match as well for such parts so as to exclude P-only parts
being marked as affected.

Note, family/model and cpu-type enumeration could be inaccurate in
virtualized environments. In a guest affected status is decided by RFDS_NO
and RFDS_CLEAR bits exposed by VMMs.

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst | 8 --------
 arch/x86/kernel/cpu/common.c                                 | 9 +++++++--
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst b/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
index 0585d02b9a6c..ad15417d39f9 100644
--- a/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
+++ b/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
@@ -29,14 +29,6 @@ Below is the list of affected Intel processors [#f1]_:
    RAPTORLAKE_S            06_BFH
    ===================  ============
 
-As an exception to this table, Intel Xeon E family parts ALDERLAKE(06_97H) and
-RAPTORLAKE(06_B7H) codenamed Catlow are not affected. They are reported as
-vulnerable in Linux because they share the same family/model with an affected
-part. Unlike their affected counterparts, they do not enumerate RFDS_CLEAR or
-CPUID.HYBRID. This information could be used to distinguish between the
-affected and unaffected parts, but it is deemed not worth adding complexity as
-the reporting is fixed automatically when these parts enumerate RFDS_NO.
-
 Mitigation
 ==========
 Intel released a microcode update that enables software to clear sensitive
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9d41f8f7267a..fa9773207175 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1206,6 +1206,11 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
 #define VULNBL_INTEL_STEPS(vfm, max_stepping, issues)		   \
 	X86_MATCH_VFM_STEPS(INTEL_##vfm, X86_STEP_MIN, max_stepping, issues)
 
+#define VULNBL_INTEL_TYPE(vfm, cpu_type, issues)			\
+	X86_MATCH_VFM_CPU_TYPE(INTEL_##vfm,				\
+			       INTEL_CPU_TYPE_##cpu_type,	\
+			       issues)
+
 #define VULNBL_AMD(family, blacklist)		\
 	VULNBL(AMD, family, X86_MODEL_ANY, blacklist)
 
@@ -1254,9 +1259,9 @@ 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_TYPE(	ALDERLAKE,	ATOM,	RFDS),
 	VULNBL_INTEL(		ALDERLAKE_L,		RFDS),
-	VULNBL_INTEL(		RAPTORLAKE,		RFDS),
+	VULNBL_INTEL_TYPE(	RAPTORLAKE,	ATOM,	RFDS),
 	VULNBL_INTEL(		RAPTORLAKE_P,		RFDS),
 	VULNBL_INTEL(		RAPTORLAKE_S,		RFDS),
 	VULNBL_INTEL(		ATOM_GRACEMONT,		RFDS),

-- 
2.34.1