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* [PATCH v5 RESEND] x86/cpu/intel: Fix the constant_tsc model check for Pentium 4
@ 2025-08-16  6:51 Suchit Karunakaran
  0 siblings, 0 replies; only message in thread
From: Suchit Karunakaran @ 2025-08-16  6:51 UTC (permalink / raw)
  To: tglx, mingo, bp, dave.hansen, hpa, darwi, sohil.mehta, peterz,
	ravi.bangoria
  Cc: skhan, linux-kernel-mentees, linux-kernel, Suchit Karunakaran,
	stable

Pentium 4's which are INTEL_P4_PRESCOTT (model 0x03) and later have
a constant TSC. This was correctly captured until commit fadb6f569b10
("x86/cpu/intel: Limit the non-architectural constant_tsc model checks").

In that commit, an error was introduced while selecting the last P4
model (0x06) as the upper bound. Model 0x06 was transposed to
INTEL_P4_WILLAMETTE, which is just plain wrong. That was presumably a
simple typo, probably just copying and pasting the wrong P4 model.

Fix the constant TSC logic to cover all later P4 models. End at
INTEL_P4_CEDARMILL which accurately corresponds to the last P4 model.

Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural constant_tsc model checks")
Cc: <stable@vger.kernel.org> # v6.15
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
---
Changes since v4:
- Updated the patch based on review suggestions

Changes since v3:
- Refined changelog

Changes since v2:
- Improved commit message

Changes since v1:
- Fixed incorrect logic

 arch/x86/kernel/cpu/intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 076eaa41b8c8..98ae4c37c93e 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 	if (c->x86_power & (1 << 8)) {
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
-	} else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
+	} else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
 		   (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 	}
-- 
2.50.1


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