From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Sean V Kelley <skelley@nvidia.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 503/641] ACPI: CPPC: Fix remaining for_each_possible_cpu() to use online CPUs
Date: Tue, 24 Feb 2026 17:23:49 -0800
Message-ID: <20260225012400.709435919@linuxfoundation.org>
In-Reply-To: <20260225012348.915798704@linuxfoundation.org>
References: <20260225012348.915798704@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sean V Kelley <skelley@nvidia.com>

[ Upstream commit 56eb0c0ed345da7815274aa821a8546a073d7e97 ]

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, send_pcc_cmd() and acpi_get_psd_map() still iterate over all
possible CPUs. In acpi_get_psd_map(), encountering an offline CPU
returns -EFAULT, causing cppc_cpufreq initialization to fail.

This breaks systems booted with "nosmt" or "nosmt=force".

Fix by using for_each_online_cpu() in both functions.

Fixes: 80b8286aeec0 ("ACPI / CPPC: support for batching CPPC requests")
Signed-off-by: Sean V Kelley <skelley@nvidia.com>
Link: https://patch.msgid.link/20260211212254.30190-1-skelley@nvidia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/acpi/cppc_acpi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index e66e20d1f31b7..b59b0100d03c5 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -362,7 +362,7 @@ static int send_pcc_cmd(int pcc_ss_id, u16 cmd)
 end:
 	if (cmd == CMD_WRITE) {
 		if (unlikely(ret)) {
-			for_each_possible_cpu(i) {
+			for_each_online_cpu(i) {
 				struct cpc_desc *desc = per_cpu(cpc_desc_ptr, i);
 
 				if (!desc)
@@ -524,7 +524,7 @@ int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data)
 	else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY)
 		cpu_data->shared_type = CPUFREQ_SHARED_TYPE_ANY;
 
-	for_each_possible_cpu(i) {
+	for_each_online_cpu(i) {
 		if (i == cpu)
 			continue;
 
-- 
2.51.0