On Wed, 6 Aug 2025 at 21:04, Suchit Karunakaran suchitkarunakaran@gmail.com wrote:

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 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

Hi Sohil, Could you please review the patch? I hope I haven't made any mistakes this time, and if there are any, it was completely unintentional and I apologise in advance.

Thanks, Suchit