Re: [PATCH] cacheinfo: don't propagate DT/ACPI error when arch supplies info (arm64)

[Pierre Gondois]

On 6/9/26 18:23, Breno Leitao wrote:
> cache_setup_properties() sets use_arch_info = true when DT/ACPI
> provide no cache nodes and the arch can derive the topology from
> CPU registers (e.g. arm64 reading CLIDR_EL1), but still returns the
> original -ENOENT. cache_shared_cpu_map_setup() bails on that error
> before the new flag can take effect, so the first CPU brought online
> always trips a misleading warning:
>
>    cacheinfo: Unable to detect cache hierarchy for CPU 0
>
> Subsequent CPUs skip cache_setup_properties() entirely because
> use_arch_info is now true, which is why only CPU0 hits it. This is
> reproducible on arm64 with the QEMU 'virt' machine, whose default DT
> has no cache nodes.
>
> Clear ret after setting use_arch_info so the caller proceeds and
> populates the shared cpu map via the arch-supplied leaves.
>
> Fixes: ef9f643a9f8b ("cacheinfo: Add use_arch[|_cache]_info field/function")
> Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
> ---
> Cc; hruben@xxxxxxxx
> ---
>   drivers/base/cacheinfo.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index 70701d3bc81c..4e11d36f127e 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -401,9 +401,18 @@ static int cache_setup_properties(unsigned int cpu)
>   	else if (!acpi_disabled)
>   		ret = cache_setup_acpi(cpu);
>   
> -	// Assume there is no cache information available in DT/ACPI from now.
> -	if (ret && use_arch_cache_info())
> +	/*
> +	 * If DT/ACPI lacks cache nodes but the arch can derive the topology
> +	 * from CPU registers (e.g. arm64 reading CLIDR_EL1), fall back to
> +	 * that path instead of propagating the error.  Otherwise the very
> +	 * first CPU processed trips a misleading "Unable to detect cache
> +	 * hierarchy" warning, because use_arch_info is only set after the
> +	 * first failure.
> +	 */

NIT: Maybe the comment is a bit long/verbose,
but maybe also not worth a v2

Reviewed-by: Pierre Gondois <pierre.gondois@xxxxxxx>

> +	if (ret && use_arch_cache_info()) {
>   		use_arch_info = true;
> +		ret = 0;
> +	}
>   
>   	return ret;
>   }
>
> ---
> base-commit: a87737435cfa134f9cdcc696ba3080759d04cf72
> change-id: 20260609-cacheinfo-b2a8d27a19ce
>
> Best regards,