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

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Date: Mon, 17 Jun 2024 02:12:14 -0700
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>
Subject: [PATCH PATCH 9/9] x86/rfds: Exclude P-only parts from the RFDS
 affected list

RFDS only affects Atom parts. Vendor/Family/Model matching in the affected
processor table makes Alderlake and Raptorlake P-only parts affected (which
are not affected in reality). This is because the affected hybrid and
E-only parts have the same Family/Model as the unaffected P-only parts.

Match CPU-type as Atom to exclude P-only parts as RFDS affected.

Note, a guest with the same Family/Model as the affected part may not have
leaf 1A enumerated to know its CPU-type, but it should not be a problem as
guest's Family/Model can anyways be inaccurate. Moreover, RFDS_NO or
RFDS_CLEAR enumeration by the VMM decides the affected status of the guest.

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                                 | 7 +++++--
 2 files changed, 5 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 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),
 
 	VULNBL_AMD(0x15, RETBLEED),
 	VULNBL_AMD(0x16, RETBLEED),

-- 
2.34.1