Re: [PATCH v2 1/3] cacheinfo: Set cache 'id' based on DT data

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Fri, 4 Jul 2025 17:38:24 +0000
James Morse <james.morse@arm.com> wrote:

> From: Rob Herring <robh@kernel.org>
> 
> Use the minimum CPU h/w id of the CPUs associated with the cache for the
> cache 'id'. This will provide a stable id value for a given system. As
> we need to check all possible CPUs, we can't use the shared_cpu_map
> which is just online CPUs. As there's not a cache to CPUs mapping in DT,
> we have to walk all CPU nodes and then walk cache levels.
> 
> The cache_id exposed to user-space has historically been 32 bits, and
> is too late to change. This value is parsed into a u32 by user-space
> libraries such as libvirt:
> https://github.com/libvirt/libvirt/blob/master/src/util/virresctrl.c#L1588
> 
> Give up on assigning cache-id's if a CPU h/w id greater than 32 bits
> is found.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Signed-off-by: Rob Herring <robh@kernel.org>
> [ ben: converted to use the __free cleanup idiom ]
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> [ morse: Add checks to give up if a value larger than 32 bits is seen. ]
> Signed-off-by: James Morse <james.morse@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>