[v5,9/9] x86/rfds: Exclude P-only parts from the RFDS affected list

Commit Message

Pawan Gupta Dec. 12, 2024, 6:58 a.m. UTC

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.

Acked-by: Dave Hansen <[e-mail]>
Signed-off-by: Pawan Gupta <[e-mail]>
---
 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(-)

Patch

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 6c45b8bed9fc..a82d6184e1d0 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1207,6 +1207,11 @@  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_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)
 
@@ -1255,9 +1260,9 @@  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),