Re: [sos-linux-dev] [PATCH v6 0/9] dax/hmem, cxl: Coordinate Soft Reserved handling with CXL and HMEM

Koralahalli Channabasappa, Smita
2026-02-12T20:02:19Z

On 2/9/2026 10:44 PM, Smita Koralahalli wrote:
> This series aims to address long-standing conflicts between HMEM and
> CXL when handling Soft Reserved memory ranges.
>
> Reworked from Dan's patch:
> https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/patch/?id=ab70c6227ee6165a562c215d9dcb4a1c55620d5d
>
> Previous work:
> https://lore.kernel.org/all/20250715180407.47426-1-Smita.KoralahalliChannabasappa@amd.com/
>
> Link to v5:
> https://lore.kernel.org/all/20260122045543.218194-1-Smita.KoralahalliChannabasappa@amd.com
>
> The series is based on branch "for-7.0/cxl-init" and base-commit is
> base-commit: bc62f5b308cbdedf29132fe96e9d591e526527e1
>

[snip]..

> [5] When CXL_BUS = m (with CXL_ACPI, CXL_PCI, CXL_PORT, CXL_MEM = m),
> DAX_CXL = m and DAX_HMEM = y the results are as expected. To validate the

Typo here, this is DAX_HMEM = m. Rest all looks good.

Thanks
Smita.

> REGISTER path, I forced REGISTER even in cases where SR completely
> overlaps the CXL region as I did not have access to a system where the
> CXL region range is smaller than the SR range.
>
> 850000000-284fffffff : Soft Reserved
> 850000000-284fffffff : CXL Window 0
> 850000000-280fffffff : region0
> 850000000-284fffffff : dax6.0
> 850000000-284fffffff : System RAM (kmem)
>
> "path":"\/platform\/hmem.6",
> "id":6,
> "size":"128.00 GiB (137.44 GB)",
> "align":2097152
>
> [ 30.897665] devm_cxl_add_dax_region: cxl_region region0: region0:
> register dax_region0
> [ 30.921015] hmem: hmem_platform probe started.
> [ 31.017946] hmem_platform hmem_platform.0: Soft Reserved not fully
> contained in CXL; using HMEM
> [ 31.056310] alloc_dev_dax_range: dax6.0: alloc range[0]:
> 0x0000000850000000:0x000000284fffffff
> [ 34.781516] cxl-dax: cxl_dax_region_init()
> [ 34.781522] cxl-dax: registering driver.
> [ 34.781523] cxl-dax: dax_hmem work flushed.
> [ 34.781549] alloc_dax_region: cxl_dax_region dax_region0: dax_region
> resource conflict for [mem 0x850000000-0x284fffffff]
> [ 34.781552] cxl_bus_probe: cxl_dax_region dax_region0: probe: -12
> [ 34.781554] cxl_dax_region dax_region0: probe with driver cxl_dax_region
> failed with error -12
>
[snip]