diff mbox series

[RFC,13/15] x86/cpu/intel: Bound the non-architectural constant_tsc model checks

Message ID 20241220213711.1892696-14-sohil.mehta@intel.com (mailing list archive)
State New
Headers show
Series Prepare for new Intel family models | expand

Commit Message

Sohil Mehta Dec. 20, 2024, 9:37 p.m. UTC 
Constant TSC has been architectural on Intel CPUs for a while. Supported
CPUs use the architectural Invariant TSC bit in CPUID.80000007. A family
model check is not required for such CPUs.

Prevent unnecessary confusion but restricting the checks and moving it
closer to the architectural check.

Invariant TSC was likely introduced around the Nehalam timeframe on the
Xeon side and Saltwell timeframe on the Atom side. (Needs confirmation)
Due to interspersed model numbers use an Ivybridge model number check to
be safe.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
---
 arch/x86/kernel/cpu/intel.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 26962a602e86..d37ef3a72234 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -210,10 +210,6 @@  static void early_init_intel(struct cpuinfo_x86 *c)
 {
 	u64 misc_enable;
 
-	if ((c->x86 == 0xf && c->x86_model >= 0x03) ||
-		(c->x86 == 0x6 && c->x86_model >= 0x0e))
-		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
-
 	if (c->x86 >= 6 && !cpu_has(c, X86_FEATURE_IA64))
 		c->microcode = intel_get_microcode_revision();
 
@@ -272,6 +268,11 @@  static void early_init_intel(struct cpuinfo_x86 *c)
 		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
 	}
 
+	/* Some older CPUs have invariant TSC but may not report it architecturally via 8000_0007 */
+	if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
+	    (c->x86_vfm >= INTEL_CORE_YONAH && c->x86_vfm <= INTEL_IVYBRIDGE))
+		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
+
 	/* Penwell and Cloverview have the TSC which doesn't sleep on S3 */
 	switch (c->x86_vfm) {
 	case INTEL_ATOM_SALTWELL_MID: