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Tue, 29 Jul 2025 21:26:27 -0700 (PDT) Received: from archlinux ([38.188.108.234]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-24058bbb554sm38795635ad.50.2025.07.29.21.26.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Jul 2025 21:26:26 -0700 (PDT) From: Suchit Karunakaran To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, darwi@linutronix.de, sohil.mehta@intel.com, peterz@infradead.org, ravi.bangoria@amd.com Cc: skhan@linuxfoundation.org, linux-kernel-mentees@lists.linux.dev, linux-kernel@vger.kernel.org, Suchit Karunakaran , stable@vger.kernel.org Subject: [PATCH v3] x86/cpu/intel: Fix the constant_tsc model check for Pentium 4s Date: Wed, 30 Jul 2025 09:56:17 +0530 Message-ID: <20250730042617.5620-1-suchitkarunakaran@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The logic to synthesize constant_tsc for Pentium 4s (Family 15) is wrong. Since INTEL_P4_PRESCOTT is numerically greater than INTEL_P4_WILLAMETTE, the logic always results in false and never sets X86_FEATURE_CONSTANT_TSC for any Pentium 4 model. The error was introduced while replacing the x86_model check with a VFM one. The original check was as follows: if ((c->x86 == 0xf && c->x86_model >= 0x03) || (c->x86 == 0x6 && c->x86_model >= 0x0e)) set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); Fix the logic to cover all Pentium 4 models from Prescott (model 3) to Cedarmill (model 6) which is the last model released in Family 15. Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural constant_tsc model checks") Cc: # v6.15 Signed-off-by: Suchit Karunakaran --- Changes since v2: - Improve commit message Changes since v1: - Fix 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..6f5bd5dbc249 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