Re: [PATCH v9 19/19] cpumask: Add enabled cpumask for present CPUs that can be brought online

From: Gavin Shan
Date: Wed May 01 2024 - 07:15:15 EST


On 5/1/24 00:24, Jonathan Cameron wrote:
From: James Morse <james.morse@xxxxxxx>

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@xxxxxxx>
Tested-by: Miguel Luis <miguel.luis@xxxxxxxxxx>
Tested-by: Vishnu Pajjuri <vishnu@xxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Jianyong Wu <jianyong.wu@xxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

---
v9: No change
---
.../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(+)


Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>