[PATCH] x86/bugs: Don't use cpu-type matching in cpu_vuln_blacklist

[PATCH] x86/bugs: Don't use cpu-type matching in cpu_vuln_blacklist

[Pawan Gupta]

Thomas Gleixner pointed out that cpu-type is a per-CPU property while
hybrid is a system property, conflating the two in the CPU matching
infrastructure is wrong. Currently, on a hybrid system x86_match_cpu()
matches any cpu-type. This works if the intent is to find the possibility
of a cpu-type in a system. But fails if matching for the cpu-type of a
given CPU.

Borislav posted a cleanup here:

  https://lore.kernel.org/all/20260703193222.GFakgORjvxwnZTPRnI@fat_crate.local

To make way for the cleanup stop matching cpu-type in cpu_vuln_blacklist.
RFDS is the only user, so drop the VULNBL_INTEL_TYPE entries and fold their
RFDS bit into the base Alder Lake (0x97) and Raptor Lake (0xB7) blacklist
entries. For now open-code cpu-type check in vulnerable_to_rfds(). In
future, if more vulnerabilities need cpu-type matching a helper can be
added.

No functional change intended.

Fixes: 722fa0dba74f ("x86/rfds: Exclude P-only parts from the RFDS affected list")
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a3df21d26460..b38126199a5b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1251,9 +1251,6 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
 #define VULNBL_INTEL_STEPS(vfm, max_stepping, issues)		   \
 	X86_MATCH_VFM_STEPS(vfm, X86_STEP_MIN, max_stepping, issues)
 
-#define VULNBL_INTEL_TYPE(vfm, cpu_type, issues)	\
-	X86_MATCH_VFM_CPU_TYPE(vfm, INTEL_CPU_TYPE_##cpu_type, issues)
-
 #define VULNBL_AMD(family, blacklist)		\
 	VULNBL(AMD, family, X86_MODEL_ANY, blacklist)
 
@@ -1316,11 +1313,9 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
 	VULNBL_INTEL_STEPS(INTEL_TIGERLAKE,	     X86_STEP_MAX,	GDS | ITS | ITS_NATIVE_ONLY),
 	VULNBL_INTEL_STEPS(INTEL_LAKEFIELD,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED),
 	VULNBL_INTEL_STEPS(INTEL_ROCKETLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
-	VULNBL_INTEL_TYPE(INTEL_ALDERLAKE,		     ATOM,	RFDS | VMSCAPE),
-	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE,	     X86_STEP_MAX,	RFDS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE_L,	     X86_STEP_MAX,	RFDS | VMSCAPE),
-	VULNBL_INTEL_TYPE(INTEL_RAPTORLAKE,		     ATOM,	RFDS | VMSCAPE),
-	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE,	     X86_STEP_MAX,	RFDS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_P,	     X86_STEP_MAX,	RFDS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_S,	     X86_STEP_MAX,	RFDS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_METEORLAKE_L,	     X86_STEP_MAX,	VMSCAPE),
@@ -1388,7 +1383,21 @@ static bool __init vulnerable_to_rfds(u64 x86_arch_cap_msr)
 		return true;
 
 	/* Only consult the blacklist when there is no enumeration: */
-	return cpu_matches(cpu_vuln_blacklist, RFDS);
+	if (!cpu_matches(cpu_vuln_blacklist, RFDS))
+		return false;
+
+	/*
+	 * ADL and RPL are affected only if they have Atom CPUs. Hybrids have
+	 * both Core and Atom CPUs. Mark unaffected when Atom CPUs are not
+	 * present.
+	 */
+	if ((boot_cpu_data.x86_model == 0x97 ||
+	     boot_cpu_data.x86_model == 0xB7) &&
+	     boot_cpu_data.topo.intel_type != INTEL_CPU_TYPE_ATOM &&
+	     !boot_cpu_has(X86_FEATURE_HYBRID_CPU))
+		return false;
+
+	return true;
 }
 
 static bool __init vulnerable_to_its(u64 x86_arch_cap_msr)

---
base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda
change-id: 20260708-cpu-type-vuln-14ded7fc0d47