linux-kernel - [tip: x86/cpu] x86/cpu/intel: Fix the constant

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Message-ID: <175588976768.1420.16910015408694101752.tip-bot2@tip-bot2>
Date: Fri, 22 Aug 2025 19:09:27 -0000
From: "tip-bot2 for Suchit Karunakaran" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Suchit Karunakaran <suchitkarunakaran@...il.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Sohil Mehta <sohil.mehta@...el.com>, stable@...r.kernel.org, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: x86/cpu] x86/cpu/intel: Fix the constant_tsc model check for Pentium 4

The following commit has been merged into the x86/cpu branch of tip:

Commit-ID:     1a77c102cee20edb2459334d8eaf3202697ac8f5
Gitweb:        https://git.kernel.org/tip/1a77c102cee20edb2459334d8eaf3202697ac8f5
Author:        Suchit Karunakaran <suchitkarunakaran@...il.com>
AuthorDate:    Sat, 16 Aug 2025 12:21:26 +05:30
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Fri, 22 Aug 2025 12:02:59 -07:00

x86/cpu/intel: Fix the constant_tsc model check for Pentium 4

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")
Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Sohil Mehta <sohil.mehta@...el.com>
Cc:stable@...r.kernel.org
Link: https://lore.kernel.org/all/20250816065126.5000-1-suchitkarunakaran%40gmail.com
---
 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 076eaa4..98ae4c3 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);
 	}