linux-kernel - [PATCH v5 09/18] ACPI: Check _STA present bit before making CPUs not present

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Date: Fri, 12 Apr 2024 15:37:10 +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 09/18] ACPI: Check _STA present bit before making CPUs not present

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

When called acpi_processor_post_eject() unconditionally make a CPU
not-present and unregisters it.

To add support for AML events where the CPU has become disabled, but
remains present, the _STA method should be checked before calling
acpi_processor_remove().

Rename acpi_processor_post_eject() acpi_processor_remove_possible(), and
check the _STA before calling.

Adding the function prototype for arch_unregister_cpu() allows the
preprocessor guards to be removed.

After this change CPUs will remain registered and visible to
user-space as offline if buggy firmware triggers an eject-request,
but doesn't clear the corresponding _STA bits after _EJ0 has been
called.

Signed-off-by: James Morse <james.morse@....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 | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 15d89f80857b..0403eddb3f80 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -462,16 +462,13 @@ static int acpi_processor_add(struct acpi_device *device,
 }
 
 /* Removal */
-static void acpi_processor_post_eject(struct acpi_device *device)
+static void acpi_processor_make_not_present(struct acpi_device *device)
 {
 	struct acpi_processor *pr;
 
 	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU))
 		return;
 
-	if (!device || !acpi_driver_data(device))
-		return;
-
 	pr = acpi_driver_data(device);
 	if (pr->id >= nr_cpu_ids)
 		goto out;
@@ -508,6 +505,29 @@ static void acpi_processor_post_eject(struct acpi_device *device)
 	kfree(pr);
 }
 
+static void acpi_processor_post_eject(struct acpi_device *device)
+{
+	struct acpi_processor *pr;
+	unsigned long long sta;
+	acpi_status status;
+
+	if (!device)
+		return;
+
+	pr = acpi_driver_data(device);
+	if (!pr || pr->id >= nr_cpu_ids || invalid_phys_cpuid(pr->phys_id))
+		return;
+
+	status = acpi_evaluate_integer(pr->handle, "_STA", NULL, &sta);
+	if (ACPI_FAILURE(status))
+		return;
+
+	if (cpu_present(pr->id) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
+		acpi_processor_make_not_present(device);
+		return;
+	}
+}
+
 #ifdef CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC
 bool __init processor_physically_present(acpi_handle handle)
 {
-- 
2.39.2