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

Pawan Gupta
2024-06-17T09:12:16Z

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@linux.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