On 4/28/26 14:53, Daniel Wagner wrote:
On Mon, Apr 27, 2026 at 05:34:16PM +0200, Sebastian Andrzej Siewior wrote:
Which driver uses cpu_possible_mask? This mask is assigned at boot time
once the kernel figured how many CPUs are possible based on ACPI or
whatever the system uses. This mask does not change.
I only see drivers/scsi/lpfc/lpfc_init.c using it. Looking at
cpu_possible_mask might not be the right thing. It is usually the same
thing as "online" except on system where ACPI thinks that something
could be added via hotplug _or_ if the admin shuts down a CPU via
cpuhotplug _or_ boots with less (there a command line option for
that).
These HBAs are used on PowerPC which supports lpar (CPUs can be added
during runtime) I am told it's properly the only driver which is caring
about this type configuration, thus a bit of an odd ball.
In case cpu_possible_mask != cpu_online_mask the intention is to
allocate memory and setup irqs for the offline CPUs?
I can't answer this. The lpfc driver has several strategies implemented
how it spreads its resources.
The intention is to setup the driver queue affinity only once (knowing
that all possible CPUs are handled correctly), avoiding a driver
reconfiguration on CPU hotplug.
Not the most efficient one, sure.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
[email protected] +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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