linux-kernel - [PATCH 2/4] ACPI: CPPC: Check _CPC validity for only the online CPUs

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Message-ID: <20251105143851.4251-3-gautham.shenoy@amd.com>
Date: Wed, 5 Nov 2025 20:08:49 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	Mario Limonciello <mario.limonciello@....com>, Yunhui Cui
	<cuiyunhui@...edance.com>, Jeremy Linton <jeremy.linton@....com>, "Viresh
 Kumar" <viresh.kumar@...aro.org>, Ionela Voinescu <ionela.voinescu@....com>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Christopher
 Harris" <chris.harris79@...il.com>, <linux-pm@...r.kernel.org>, "Gautham R.
 Shenoy" <gautham.shenoy@....com>
Subject: [PATCH 2/4] ACPI: CPPC: Check _CPC validity for only the online CPUs

per_cpu(cpc_desc_ptr, cpu) object is initialized for only the online
CPUs via acpi_soft_cpu_online() --> __acpi_processor_start() -->
acpi_cppc_processor_probe().

However the function acpi_cpc_valid() checks for the validity of the
_CPC object for all the present CPUs. This breaks when the kernel is
booted with "nosmt=force".

Hence check the validity of the _CPC objects of only the online CPUs.

Fixes: 2aeca6bd0277 ("ACPI: CPPC: Check present CPUs for determining _CPC is valid")
Reported-by: Christopher Harris <chris.harris79@...il.com>
Closes: https://lore.kernel.org/lkml/CAM+eXpdDT7KjLV0AxEwOLkSJ2QtrsvGvjA2cCHvt1d0k2_C4Cw@mail.gmail.com/
Suggested-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@....com>
---
 drivers/acpi/cppc_acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index ab4651205e8a..50e6348b511f 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -460,7 +460,7 @@ bool acpi_cpc_valid(void)
 	if (acpi_disabled)
 		return false;
 
-	for_each_present_cpu(cpu) {
+	for_each_online_cpu(cpu) {
 		cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
 		if (!cpc_ptr)
 			return false;
-- 
2.34.1