linux-kernel - [PATCH v5 10/18] ACPI: Warn when the present bit changes but the feature is not enabled

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Date: Fri, 12 Apr 2024 15:37:11 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: <linux-pm@...r.kernel.org>, <loongarch@...ts.linux.dev>,
	<linux-acpi@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<kvmarm@...ts.linux.dev>, <x86@...nel.org>, Russell King
	<linux@...linux.org.uk>, "Rafael J . Wysocki" <rafael@...nel.org>, Miguel
 Luis <miguel.luis@...cle.com>, James Morse <james.morse@....com>, Salil Mehta
	<salil.mehta@...wei.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
CC: <linuxarm@...wei.com>, <justin.he@....com>, <jianyong.wu@....com>
Subject: [PATCH v5 10/18] ACPI: Warn when the present bit changes but the feature is not enabled

From: James Morse <james.morse@....com>

ACPI firmware can trigger the events to add and remove CPUs, but the
OS may not support this.

Print an error message when this happens.

This gives early warning on arm64 systems that don't support
CONFIG_ACPI_HOTPLUG_PRESENT_CPU, as making CPUs not present has
side effects for other parts of the system.

Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Gavin Shan <gshan@...hat.com>
Tested-by: Miguel Luis <miguel.luis@...cle.com>
Tested-by: Vishnu Pajjuri <vishnu@...amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@....com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
---
v5: No change
---
 drivers/acpi/acpi_processor.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 0403eddb3f80..3fb167ee9807 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -187,8 +187,10 @@ static int acpi_processor_make_present(struct acpi_processor *pr)
 {
 	int ret;
 
-	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU))
+	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU)) {
+		pr_err_once("Changing CPU present bit is not supported\n");
 		return -ENODEV;
+	}
 
 	if (invalid_phys_cpuid(pr->phys_id))
 		return -ENODEV;
@@ -466,8 +468,10 @@ static void acpi_processor_make_not_present(struct acpi_device *device)
 {
 	struct acpi_processor *pr;
 
-	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU))
+	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU)) {
+		pr_err_once("Changing CPU present bit is not supported");
 		return;
+	}
 
 	pr = acpi_driver_data(device);
 	if (pr->id >= nr_cpu_ids)
-- 
2.39.2