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

[Koralahalli Channabasappa, Smita]

On 1/22/2026 8:39 AM, Jonathan Cameron wrote:
> On Thu, 22 Jan 2026 04:55:43 +0000
> Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx> wrote:
>
> > Reworked from a patch by Alison Schofield <alison.schofield@xxxxxxxxx>
> >
> > 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@xxxxxxxxx/
> > Co-developed-by: Alison Schofield <alison.schofield@xxxxxxxxx>
> > Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
> > Co-developed-by: Zhijian Li <lizhijian@xxxxxxxxxxx>
> > Signed-off-by: Zhijian Li <lizhijian@xxxxxxxxxxx>
> > Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
> > Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> > Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> 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.

Sure, I will make the changes.

Thanks
Smita
> > +	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) {