Re: [PATCH v3 3/3] cxl: Add memory hotplug notifier for cxl region

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

Jonathan Cameron wrote:
> On Mon, 08 Jan 2024 14:49:03 +0800
> "Huang, Ying" <ying.huang@intel.com> wrote:
> 
> > Dave Jiang <dave.jiang@intel.com> writes:
> > 
> > > When the CXL region is formed, the driver would computed the performance
> > > data for the region. However this data is not available at the node data
> > > collection that has been populated by the HMAT during kernel
> > > initialization. Add a memory hotplug notifier to update the performance
> > > data to the node hmem_attrs to expose the newly calculated region
> > > performance data. The CXL region is created under specific CFMWS. The
> > > node for the CFMWS is created during SRAT parsing by acpi_parse_cfmws().
> > > Additional regions may overwrite the initial data, but since this is
> > > for the same proximity domain it's a don't care for now.
> > >
> > > 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
> > > ndoe_set_perf_attrs() for the various attributes where nodeX is matched
> > > to the proximity domain of the CXL region.
> 
> As per discussion below.  Why is access1 not also relevant for CXL memory?
> (it's probably more relevant than access0 in many cases!)
> 
> For historical references, I wanted access0 to be the CPU only one, but
> review feedback was that access0 was already defined as 'initiator based'
> so we couldn't just make the 0 indexed one the case most people care about.
> Hence we grew access1 to cover the CPU only case which most software cares
> about.

Oh I had not followed any of that evolution of the original
HMEM_REPORTING code that specific indexes had different initiator
meanings vs just being a performance ordinal.