linux-kernel - Re: [PATCH V6 10/18] cxl/mem: Refactor cxl pmem region auto-assembling

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Message-ID: <6979522dc1916_1d331009@dwillia2-mobl4.notmuch>
Date: Tue, 27 Jan 2026 16:02:53 -0800
From: <dan.j.williams@...el.com>
To: Neeraj Kumar <s.neeraj@...sung.com>, <linux-cxl@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<gost.dev@...sung.com>
CC: <a.manzanares@...sung.com>, <vishak.g@...sung.com>,
	<neeraj.kernel@...il.com>, Neeraj Kumar <s.neeraj@...sung.com>
Subject: Re: [PATCH V6 10/18] cxl/mem: Refactor cxl pmem region
 auto-assembling

Neeraj Kumar wrote:
> In 84ec985944ef3, devm_cxl_add_nvdimm() sequence was changed and called
> before devm_cxl_add_endpoint(). It's because cxl pmem region auto-assembly
> used to get called at last in cxl_endpoint_port_probe(), which requires
> cxl_nvd presence.

What?

> For cxl region persistency, region creation happens during nvdimm_probe
> which need the completion of endpoint probe.
> 
> In order to accommodate both cxl pmem region auto-assembly and cxl region
> persistency, refactored following
> 
> 1. Re-Sequence devm_cxl_add_nvdimm() after devm_cxl_add_endpoint(). This
>    will be called only after successful completion of endpoint probe.
> 
> 2. Create cxl_region_discovery() which performs pmem region
>    auto-assembly and remove cxl pmem region auto-assembly from
>    cxl_endpoint_port_probe()
> 
> 3. Register cxl_region_discovery() with devm_cxl_add_memdev() which gets
>    called during cxl_pci_probe() in context of cxl_mem_probe()
> 
> 4. As cxlmd->attach->probe() calls registered cxl_region_discovery(), so
>    move devm_cxl_add_nvdimm() before cxlmd->attach->probe(). It guarantees
>    both the completion of endpoint probe and cxl_nvd presence before
>    calling cxlmd->attach->probe().

This does not make sense. The whole point of having
devm_cxl_add_nvdimm() before devm_cxl_add_endpoint() is so that the
typical region discovery path can consider pre-existing decoder settings
*or* nvdimm labels in its assembly decisions.

I would be surprised if this passes existing region assembly and
ordering tests.

This reads like "do not understand current ordering, change it for thin
reasons".