linux-kernel - Re: [PATCH v5 7/7] dax/hmem: Reintroduce Soft Reserved ranges back into the iomem tree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260122163948.00007ff6@huawei.com>
Date: Thu, 22 Jan 2026 16:39:48 +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
 Wilcox" <willy@...radead.org>, Jan Kara <jack@...e.cz>, "Rafael J . Wysocki"
	<rafael@...nel.org>, Len Brown <len.brown@...el.com>, Pavel Machek
	<pavel@...nel.org>, Li Ming <ming.li@...omail.com>, Jeff Johnson
	<jeff.johnson@....qualcomm.com>, Ying Huang <huang.ying.caritas@...il.com>,
	Yao Xingtao <yaoxt.fnst@...itsu.com>, "Peter Zijlstra"
	<peterz@...radead.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nathan Fontenot <nathan.fontenot@....com>, Terry Bowman
	<terry.bowman@....com>, Robert Richter <rrichter@....com>, Benjamin Cheatham
	<benjamin.cheatham@....com>, Zhijian Li <lizhijian@...itsu.com>, Borislav
 Petkov <bp@...en8.de>, Tomasz Wolski <tomasz.wolski@...itsu.com>
Subject: Re: [PATCH v5 7/7] dax/hmem: Reintroduce Soft Reserved ranges back
 into the iomem tree

On Thu, 22 Jan 2026 04:55:43 +0000
Smita Koralahalli <Smita.KoralahalliChannabasappa@....com> wrote:

> Reworked from a patch by Alison Schofield <alison.schofield@...el.com>
> 
> Reintroduce Soft Reserved range into the iomem_resource tree for HMEM
> to consume.
> 
> This restores visibility in /proc/iomem for ranges actively in use, while
> avoiding the early-boot conflicts that occurred when Soft Reserved was
> published into iomem before CXL window and region discovery.
> 
> Link: https://lore.kernel.org/linux-cxl/29312c0765224ae76862d59a17748c8188fb95f1.1692638817.git.alison.schofield@intel.com/
> Co-developed-by: Alison Schofield <alison.schofield@...el.com>
> Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> Co-developed-by: Zhijian Li <lizhijian@...itsu.com>
> Signed-off-by: Zhijian Li <lizhijian@...itsu.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>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
A few minor things from a fresh read.
> ---
>  drivers/dax/hmem/hmem.c | 32 +++++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
> index bcb57d8678d7..f3ef4faf158f 100644
> --- a/drivers/dax/hmem/hmem.c
> +++ b/drivers/dax/hmem/hmem.c
> @@ -64,6 +64,34 @@ struct dax_defer_work {
>  	struct work_struct work;
>  };
>  
> +static void remove_soft_reserved(void *r)
> +{
> +	remove_resource(r);
> +	kfree(r);
> +}
> +
> +static int add_soft_reserve_into_iomem(struct device *host,
> +				       const struct resource *res)
> +{
> +	struct resource *soft __free(kfree) =
> +		kzalloc(sizeof(*soft), GFP_KERNEL);

On one line. I think it's exactly 80 chars.

> +	int rc;
> +
The declaration and check should be together. For __free stuff inline declarations
are preferred.

You fully assign it so kmalloc is all that's needed.
	
	
	struct resource *soft __free(kfree) = kzalloc(sizeof(*soft), GFP_KERNEL);
	if (!soft)

If not, just switch the two declarations.

> +	if (!soft)
> +		return -ENOMEM;
> +
> +	*soft = DEFINE_RES_NAMED_DESC(res->start, (res->end - res->start + 1),
> +				      "Soft Reserved", IORESOURCE_MEM,
> +				      IORES_DESC_SOFT_RESERVED);
> +
> +	rc = insert_resource(&iomem_resource, soft);
> +	if (rc)
> +		return rc;
> +
> +	return devm_add_action_or_reset(host, remove_soft_reserved,
> +					no_free_ptr(soft));
> +}
> +
>  static int hmem_register_device(struct device *host, int target_nid,
>  				const struct resource *res)
>  {
> @@ -94,7 +122,9 @@ static int hmem_register_device(struct device *host, int target_nid,
>  	if (rc != REGION_INTERSECTS)
>  		return 0;
>  
> -	/* TODO: Add Soft-Reserved memory back to iomem */
> +	rc = add_soft_reserve_into_iomem(host, res);
> +	if (rc)
> +		return rc;
>  
>  	id = memregion_alloc(GFP_KERNEL);
>  	if (id < 0) {