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From: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
To: linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
	linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-riscv@lists.infradead.org, kvmarm@lists.linux.dev,
	x86@kernel.org, acpica-devel@lists.linuxfoundation.org,
	linux-csky@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org
Cc: Salil Mehta <salil.mehta@huawei.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	jianyong.wu@arm.com, justin.he@arm.com,
	James Morse <james.morse@arm.com>,
	Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: [PATCH RFC v4 15/15] cpumask: Add enabled cpumask for present CPUs that can be brought online
Date: Wed, 31 Jan 2024 16:50:53 +0000	[thread overview]
Message-ID: <E1rVDnZ-0027Zl-Kr@rmk-PC.armlinux.org.uk> (raw)
In-Reply-To: <Zbp5xzmFhKDAgHws@shell.armlinux.org.uk>

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

The 'offline' file in sysfs shows all offline CPUs, including those
that aren't present. User-space is expected to remove not-present CPUs
from this list to learn which CPUs could be brought online.

CPUs can be present but not-enabled. These CPUs can't be brought online
until the firmware policy changes, which comes with an ACPI notification
that will register the CPUs.

With only the offline and present files, user-space is unable to
determine which CPUs it can try to bring online. Add a new CPU mask
that shows this based on all the registered CPUs.

Signed-off-by: James Morse <james.morse@arm.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
Changes since RFCv3 (smaller series);
 * Added Documentation/ABI/testing/sysfs-devices-system-cpu entry
---
 .../ABI/testing/sysfs-devices-system-cpu      |  6 +++++
 drivers/base/cpu.c                            | 10 ++++++++
 include/linux/cpumask.h                       | 25 +++++++++++++++++++
 kernel/cpu.c                                  |  3 +++
 4 files changed, 44 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index a1db6db47505..59482c10e0ad 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -693,3 +693,9 @@ Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
 		(RO) indicates whether or not the kernel directly supports
 		modifying the crash elfcorehdr for CPU hot un/plug and/or
 		on/offline changes.
+
+What:		/sys/devices/system/cpu/enabled
+Date:		Nov 2022
+Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:
+		(RO) the list of CPUs that can be brought online.
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 13d052bf13f4..a6e96a0a92b7 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -95,6 +95,7 @@ void unregister_cpu(struct cpu *cpu)
 {
 	int logical_cpu = cpu->dev.id;
 
+	set_cpu_enabled(logical_cpu, false);
 	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
 
 	device_unregister(&cpu->dev);
@@ -273,6 +274,13 @@ static ssize_t print_cpus_offline(struct device *dev,
 }
 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 
+static ssize_t print_cpus_enabled(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(cpu_enabled_mask));
+}
+static DEVICE_ATTR(enabled, 0444, print_cpus_enabled, NULL);
+
 static ssize_t print_cpus_isolated(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
@@ -413,6 +421,7 @@ int register_cpu(struct cpu *cpu, int num)
 	register_cpu_under_node(num, cpu_to_node(num));
 	dev_pm_qos_expose_latency_limit(&cpu->dev,
 					PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
+	set_cpu_enabled(num, true);
 
 	return 0;
 }
@@ -494,6 +503,7 @@ static struct attribute *cpu_root_attrs[] = {
 	&cpu_attrs[2].attr.attr,
 	&dev_attr_kernel_max.attr,
 	&dev_attr_offline.attr,
+	&dev_attr_enabled.attr,
 	&dev_attr_isolated.attr,
 #ifdef CONFIG_NO_HZ_FULL
 	&dev_attr_nohz_full.attr,
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index cfb545841a2c..cc72a0887f04 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -92,6 +92,7 @@ static inline void set_nr_cpu_ids(unsigned int nr)
  *
  *     cpu_possible_mask- has bit 'cpu' set iff cpu is populatable
  *     cpu_present_mask - has bit 'cpu' set iff cpu is populated
+ *     cpu_enabled_mask  - has bit 'cpu' set iff cpu can be brought online
  *     cpu_online_mask  - has bit 'cpu' set iff cpu available to scheduler
  *     cpu_active_mask  - has bit 'cpu' set iff cpu available to migration
  *
@@ -124,11 +125,13 @@ static inline void set_nr_cpu_ids(unsigned int nr)
 
 extern struct cpumask __cpu_possible_mask;
 extern struct cpumask __cpu_online_mask;
+extern struct cpumask __cpu_enabled_mask;
 extern struct cpumask __cpu_present_mask;
 extern struct cpumask __cpu_active_mask;
 extern struct cpumask __cpu_dying_mask;
 #define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask)
 #define cpu_online_mask   ((const struct cpumask *)&__cpu_online_mask)
+#define cpu_enabled_mask   ((const struct cpumask *)&__cpu_enabled_mask)
 #define cpu_present_mask  ((const struct cpumask *)&__cpu_present_mask)
 #define cpu_active_mask   ((const struct cpumask *)&__cpu_active_mask)
 #define cpu_dying_mask    ((const struct cpumask *)&__cpu_dying_mask)
@@ -993,6 +996,7 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS);
 #else
 #define for_each_possible_cpu(cpu) for_each_cpu((cpu), cpu_possible_mask)
 #define for_each_online_cpu(cpu)   for_each_cpu((cpu), cpu_online_mask)
+#define for_each_enabled_cpu(cpu)   for_each_cpu((cpu), cpu_enabled_mask)
 #define for_each_present_cpu(cpu)  for_each_cpu((cpu), cpu_present_mask)
 #endif
 
@@ -1015,6 +1019,15 @@ set_cpu_possible(unsigned int cpu, bool possible)
 		cpumask_clear_cpu(cpu, &__cpu_possible_mask);
 }
 
+static inline void
+set_cpu_enabled(unsigned int cpu, bool can_be_onlined)
+{
+	if (can_be_onlined)
+		cpumask_set_cpu(cpu, &__cpu_enabled_mask);
+	else
+		cpumask_clear_cpu(cpu, &__cpu_enabled_mask);
+}
+
 static inline void
 set_cpu_present(unsigned int cpu, bool present)
 {
@@ -1096,6 +1109,7 @@ static __always_inline unsigned int num_online_cpus(void)
 	return raw_atomic_read(&__num_online_cpus);
 }
 #define num_possible_cpus()	cpumask_weight(cpu_possible_mask)
+#define num_enabled_cpus()	cpumask_weight(cpu_enabled_mask)
 #define num_present_cpus()	cpumask_weight(cpu_present_mask)
 #define num_active_cpus()	cpumask_weight(cpu_active_mask)
 
@@ -1104,6 +1118,11 @@ static inline bool cpu_online(unsigned int cpu)
 	return cpumask_test_cpu(cpu, cpu_online_mask);
 }
 
+static inline bool cpu_enabled(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_enabled_mask);
+}
+
 static inline bool cpu_possible(unsigned int cpu)
 {
 	return cpumask_test_cpu(cpu, cpu_possible_mask);
@@ -1128,6 +1147,7 @@ static inline bool cpu_dying(unsigned int cpu)
 
 #define num_online_cpus()	1U
 #define num_possible_cpus()	1U
+#define num_enabled_cpus()	1U
 #define num_present_cpus()	1U
 #define num_active_cpus()	1U
 
@@ -1141,6 +1161,11 @@ static inline bool cpu_possible(unsigned int cpu)
 	return cpu == 0;
 }
 
+static inline bool cpu_enabled(unsigned int cpu)
+{
+	return cpu == 0;
+}
+
 static inline bool cpu_present(unsigned int cpu)
 {
 	return cpu == 0;
diff --git a/kernel/cpu.c b/kernel/cpu.c
index e6ec3ba4950b..23b5568fb378 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -3117,6 +3117,9 @@ EXPORT_SYMBOL(__cpu_possible_mask);
 struct cpumask __cpu_online_mask __read_mostly;
 EXPORT_SYMBOL(__cpu_online_mask);
 
+struct cpumask __cpu_enabled_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_enabled_mask);
+
 struct cpumask __cpu_present_mask __read_mostly;
 EXPORT_SYMBOL(__cpu_present_mask);
 
-- 
2.30.2


      parent reply	other threads:[~2024-01-31 16:56 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-31 16:48 [RFC PATCH v4 00/15] ACPI/arm64: add support for virtual cpu hotplug Russell King (Oracle)
2024-01-31 16:49 ` [PATCH RFC v4 01/15] ACPI: Only enumerate enabled (or functional) processor devices Russell King
2024-01-31 17:25   ` Miguel Luis
2024-02-15 20:10   ` Rafael J. Wysocki
2024-02-19  9:45     ` Jonathan Cameron
2024-02-20 11:30     ` Russell King (Oracle)
2024-02-21 13:01   ` Rafael J. Wysocki
2024-01-31 16:49 ` [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from acpi_processor_get_info() Russell King
2024-02-15 19:22   ` Rafael J. Wysocki
2024-02-20 11:27     ` Russell King (Oracle)
2024-02-20 15:13       ` Russell King (Oracle)
2024-02-20 16:24         ` Jonathan Cameron
2024-02-20 19:59           ` Rafael J. Wysocki
2024-02-21 12:04             ` Rafael J. Wysocki
2024-02-20 20:59     ` Thomas Gleixner
2024-03-22 18:53     ` Jonathan Cameron
2024-04-10 12:43       ` Jonathan Cameron
2024-04-10 13:28         ` Rafael J. Wysocki
2024-04-10 13:50           ` Jonathan Cameron
2024-04-10 14:19             ` Rafael J. Wysocki
2024-04-10 15:58               ` Jonathan Cameron
2024-04-10 18:56             ` Russell King (Oracle)
2024-04-10 19:08               ` Rafael J. Wysocki
2024-04-10 21:07                 ` Jonathan Cameron
2024-01-31 16:49 ` [PATCH RFC v4 03/15] ACPI: Move acpi_bus_trim_one() before acpi_scan_hot_remove() Russell King
2024-01-31 16:49 ` [PATCH RFC v4 04/15] ACPI: Rename acpi_processor_hotadd_init and remove pre-processor guards Russell King
2024-01-31 16:50 ` [PATCH RFC v4 05/15] ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug Russell King
2024-01-31 16:50 ` [PATCH RFC v4 06/15] ACPI: convert acpi_processor_post_eject() to use IS_ENABLED() Russell King (Oracle)
2024-01-31 16:50 ` [PATCH RFC v4 07/15] ACPI: Check _STA present bit before making CPUs not present Russell King
2024-01-31 16:50 ` [PATCH RFC v4 08/15] ACPI: Warn when the present bit changes but the feature is not enabled Russell King
2024-01-31 16:50 ` [PATCH RFC v4 09/15] arm64: acpi: Move get_cpu_for_acpi_id() to a header Russell King
2024-01-31 16:50 ` [PATCH RFC v4 10/15] irqchip/gic-v3: Don't return errors from gic_acpi_match_gicc() Russell King
2024-02-02 16:44   ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 11/15] irqchip/gic-v3: Add support for ACPI's disabled but 'online capable' CPUs Russell King
2024-02-02 16:47   ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 12/15] arm64: psci: Ignore DENIED CPUs Russell King
2024-04-11 11:35   ` Jonathan Cameron
2024-04-11 13:25     ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 13/15] ACPI: add support to (un)register CPUs based on the _STA enabled bit Russell King
2024-01-31 16:50 ` [PATCH RFC v4 14/15] arm64: document virtual CPU hotplug's expectations Russell King
2024-02-02 17:04   ` Jonathan Cameron
2024-01-31 16:50 ` Russell King [this message]

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