Smita Koralahalli wrote: > Stop creating cxl_dax during cxl_region_probe(). Early DAX registration > can online memory before ownership of Soft Reserved ranges is finalized. > This makes it difficult to tear down regions later when HMEM determines > that a region should not claim that range. > > Introduce a register_dax flag in struct cxl_region_params and gate DAX > registration on this flag. Leave probe time registration disabled for > regions discovered during early CXL enumeration; set the flag only for > regions created dynamically at runtime to preserve existing behaviour. > > This patch prepares the region code for later changes where cxl_dax > setup occurs from the HMEM path only after ownership arbitration > completes.
This seems backwards to me. The dax subsystem knows when it wants to move ahead with CXL or not, dax_cxl_mode is that indicator. So, just share that variable with drivers/dax/cxl.c, arrange for cxl_dax_region_probe() to fail while waiting for initial CXL probing to succeed. Once that point is reached move dax_cxl_mode to DAX_CXL_MODE_DROP, which means drop the hmem alias, and go with the real-deal CXL region. Rescan the dax-bus to retry cxl_dax_region_probe(). No need to bother 'struct cxl_region' with a 'dax' flag, it just registers per normal and lets the dax-subsystem handle accepting / rejecting. Now, we do need a mechanism from dax-to-cxl to trigger region removal in the DAX_CXL_MODE_REGISTER case (proceed with the hmem registration), but that is separate from blocking the attachment of dax to CXL regions. Keep all that complexity local to dax.
