Re: [PATCH v3 13/25] cxl/region: Add sparse DAX region support

Jonathan Cameron
2024-08-23T16:59:42Z

On Fri, 16 Aug 2024 09:44:21 -0500
ira.weiny@intel.com wrote:

> From: Navneet Singh <navneet.singh@intel.com>
>
> Dynamic Capacity CXL regions must allow memory to be added or removed
> dynamically. In addition to the quantity of memory available the
> location of the memory within a DC partition is dynamic based on the
> extents offered by a device. CXL DAX regions must accommodate the
> sparseness of this memory in the management of DAX regions and devices.
>
> Introduce the concept of a sparse DAX region. Add a create_dc_region()
> sysfs entry to create such regions. Special case DC capable regions to
> create a 0 sized seed DAX device to maintain compatibility which
> requires a default DAX device to hold a region reference.
>
> Indicate 0 byte available capacity until such time that capacity is
> added.
>
> Sparse regions complicate the range mapping of dax devices. There is no
> known use case for range mapping on sparse regions. Avoid the
> complication by preventing range mapping of dax devices on sparse
> regions.
>
> Interleaving is deferred for now. Add checks.
>
> Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

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