Re: [PATCH v2 1/5] cxl: Remove the CXL_DECODER_MIXED mistake

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

On Wed, 22 Jan 2025 00:59:16 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> CXL_DECODER_MIXED is a safety mechanism introduced for the case where
> platform firmware has programmed an endpoint decoder that straddles a
> DPA partition boundary. While the kernel is careful to only allocate DPA
> capacity within a single partition there is no guarantee that platform
> firmware, or anything that touched the device before the current kernel,
> gets that right.
> 
> However, __cxl_dpa_reserve() will never get to the CXL_DECODER_MIXED
> designation because of the way it tracks partition boundaries. A
> request_resource() that spans ->ram_res and ->pmem_res fails with the
> following signature:
> 
>     __cxl_dpa_reserve: cxl_port endpoint15: decoder15.0: failed to reserve allocation
> 
> CXL_DECODER_MIXED is dead defensive programming after the driver has
> already given up on the device. It has never offered any protection in
> practice, just delete it.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>