Re: [PATCH v7 7/7] dax/hmem: Reintroduce Soft Reserved ranges back into the iomem tree

["Koralahalli Channabasappa, Smita" <skoralah@amd.com>]

On 3/19/2026 7:35 AM, Jonathan Cameron wrote:
> On Thu, 19 Mar 2026 01:15:00 +0000
> Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> wrote:
> 
>> Reworked from a patch by Alison Schofield <alison.schofield@intel.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@intel.com>
>> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
>> Co-developed-by: Zhijian Li <lizhijian@fujitsu.com>
>> Signed-off-by: Zhijian Li <lizhijian@fujitsu.com>
>> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
>> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> One minor update needed as kmalloc_obj() has shown up in meantime.
> 
> Thanks
> 
> Jonathan
>> ---
>>   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 8c574123bd3b..15e462589b92 100644
>> --- a/drivers/dax/hmem/hmem.c
>> +++ b/drivers/dax/hmem/hmem.c
>> @@ -72,6 +72,34 @@ void dax_hmem_flush_work(void)
>>   }
>>   EXPORT_SYMBOL_GPL(dax_hmem_flush_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)
>> +{
>> +	int rc;
>> +
>> +	struct resource *soft __free(kfree) =
>> +		kmalloc(sizeof(*res), GFP_KERNEL);
> 
> Update to
> 
> 	struct resource *soft __free(kfree) = kmalloc_obj(*soft);
> 
> Got added in 7.0 with lots of call sites updated via scripting.
> 
> Not sure why this had sizeof(*res) rather than sizeof(*soft).
> Same type but should have been soft!  If nothing else that would
> probably have broken the scripts looking for where we should
> be using kmalloc_obj().

Okay I will update it. sizeof(*res) was a typo from my end. Sorry.
Will change to kmalloc_obj().

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) {
>