Re: [PATCH v3 4/4] cxl/region: Add inject and clear poison by region offset

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Sat, 12 Jul 2025 19:37:57 -0700
alison.schofield@intel.com wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> Add CXL region debugfs attributes to inject and clear poison based
> on an offset into the region. These new interfaces allow users to
> operate on poison at the region level without needing to resolve
> Device Physical Addresses (DPA) or target individual memdevs.
> 
> The implementation uses a new helper, region_offset_to_dpa_result()
> that applies decoder interleave logic, including XOR-based address
> decoding when applicable. Note that XOR decodes rely on driver
> internal xormaps which are not exposed to userspace. So, this support
> is not only a simplification of poison operations that could be done
> using existing per memdev operations, but also it enables this
> functionality for XOR interleaved regions for the first time.
> 
> New debugfs attributes are added in /sys/kernel/debug/cxl/regionX/:
> inject_poison and clear_poison. These are only exposed if all memdevs
> participating in the region support both inject and clear commands,
> ensuring consistent and reliable behavior across multi-device regions.
> 
> If tracing is enabled, these operations are logged as cxl_poison
> events in /sys/kernel/tracing/trace.
> 
> The ABI documentation warns users of the significant risks that
> come with using these capabilities.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>