linux-kernel - Re: [PATCH v5 1/7] dax/hmem: Request cxl_acpi and cxl

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Message-ID: <20260122161639.00004dd3@huawei.com>
Date: Thu, 22 Jan 2026 16:16:39 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-fsdevel@...r.kernel.org>,
	<linux-pm@...r.kernel.org>, Ard Biesheuvel <ardb@...nel.org>, "Alison
 Schofield" <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Yazen Ghannam <yazen.ghannam@....com>, "Dave
 Jiang" <dave.jiang@...el.com>, Davidlohr Bueso <dave@...olabs.net>, "Matthew
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 Petkov <bp@...en8.de>, Tomasz Wolski <tomasz.wolski@...itsu.com>
Subject: Re: [PATCH v5 1/7] dax/hmem: Request cxl_acpi and cxl_pci before
 walking Soft Reserved ranges

On Thu, 22 Jan 2026 04:55:37 +0000
Smita Koralahalli <Smita.KoralahalliChannabasappa@....com> wrote:

> From: Dan Williams <dan.j.williams@...el.com>
> 
> Ensure cxl_acpi has published CXL Window resources before HMEM walks Soft
> Reserved ranges.
> 
> Replace MODULE_SOFTDEP("pre: cxl_acpi") with an explicit, synchronous
> request_module("cxl_acpi"). MODULE_SOFTDEP() only guarantees eventual
> loading, it does not enforce that the dependency has finished init
> before the current module runs. This can cause HMEM to start before
> cxl_acpi has populated the resource tree, breaking detection of overlaps
> between Soft Reserved and CXL Windows.
> 
> Also, request cxl_pci before HMEM walks Soft Reserved ranges. Unlike
> cxl_acpi, cxl_pci attach is asynchronous and creates dependent devices
> that trigger further module loads. Asynchronous probe flushing
> (wait_for_device_probe()) is added later in the series in a deferred
> context before HMEM makes ownership decisions for Soft Reserved ranges.
> 
> Add an additional explicit Kconfig ordering so that CXL_ACPI and CXL_PCI
> must be initialized before DEV_DAX_HMEM. This prevents HMEM from consuming
> Soft Reserved ranges before CXL drivers have had a chance to claim them.
> 
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>