Re: [PATCH v7 12/12] cxl/region: Deal with numa nodes not enumerated by SRAT

[Dan Williams <dan.j.williams@intel.com>]

Dave Jiang wrote:
> For the numa nodes that are not created by SRAT, no memory_target is
> allocated and is not managed by the HMAT_REPORTING code. Therefore
> hmat_callback() memory hotplug notifier will exit early on those NUMA
> nodes. The CXL memory hotplug notifier will need to call
> node_set_perf_attrs() directly in order to setup the access sysfs
> attributes.
> 
> In acpi_numa_init(), the last proximity domain (pxm) id created by SRAT is
> stored. Add a helper function acpi_node_backed_by_real_pxm() in order to
> check if a NUMA node id is defined by SRAT or created by CFMWS.
> 
> node_set_perf_attrs() symbol is exported to allow update of perf attribs
> for a node. The sysfs path of
> /sys/devices/system/node/nodeX/access0/initiators/* is created by
> node_set_perf_attrs() for the various attributes where nodeX is matched
> to the NUMA node of the CXL region.
> 
> Cc: Rafael J. Wysocki <rafael@kernel.org>
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
> v7:
> - Fix typo is commit log. (Jonathan)
> ---
>  drivers/acpi/numa/srat.c  | 11 +++++++++++
>  drivers/base/node.c       |  1 +
>  drivers/cxl/core/cdat.c   |  5 +++++
>  drivers/cxl/core/core.h   |  1 +
>  drivers/cxl/core/region.c |  7 ++++++-
>  include/linux/acpi.h      |  9 +++++++++
>  6 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
> index 0214518fc582..e45e64993c50 100644
> --- a/drivers/acpi/numa/srat.c
> +++ b/drivers/acpi/numa/srat.c
> @@ -29,6 +29,8 @@ static int node_to_pxm_map[MAX_NUMNODES]
>  unsigned char acpi_srat_revision __initdata;
>  static int acpi_numa __initdata;
>  
> +static int last_real_pxm;
> +
>  void __init disable_srat(void)
>  {
>  	acpi_numa = -1;
> @@ -536,6 +538,7 @@ int __init acpi_numa_init(void)
>  		if (node_to_pxm_map[i] > fake_pxm)
>  			fake_pxm = node_to_pxm_map[i];
>  	}
> +	last_real_pxm = fake_pxm;
>  	fake_pxm++;
>  	acpi_table_parse_cedt(ACPI_CEDT_TYPE_CFMWS, acpi_parse_cfmws,
>  			      &fake_pxm);
> @@ -547,6 +550,14 @@ int __init acpi_numa_init(void)
>  	return 0;
>  }
>  
> +bool acpi_node_backed_by_real_pxm(int nid)
> +{
> +	int pxm = node_to_pxm(nid);
> +
> +	return pxm <= last_real_pxm;
> +}
> +EXPORT_SYMBOL_GPL(acpi_node_backed_by_real_pxm);

I quibble with this naming because it is not about "real" vs "fake" is
about HMAT decorated PXMs vs not, but I do not want to hold up v6.9
consideration for this quibble.

It can be addressed when / if cxl_need_node_perf_attrs_update() ever
interoperates with a non ACPI platform.