linux-kernel - Re: [PATCH v3 1/4] kernel/resource: Provide mem region release for SOFT RESERVES

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Message-ID: <04dac478-f734-4fb9-a792-d3f11be79657@amd.com>
Date: Thu, 10 Apr 2025 09:49:33 -0500
From: "Bowman, Terry" <terry.bowman@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dave@...olabs.net, dave.jiang@...el.com, alison.schofield@...el.com,
 vishal.l.verma@...el.com, ira.weiny@...el.com, dan.j.williams@...el.com,
 willy@...radead.org, jack@...e.cz, rafael@...nel.org, len.brown@...el.com,
 pavel@....cz, ming.li@...omail.com, nathan.fontenot@....com,
 Smita.KoralahalliChannabasappa@....com, huang.ying.caritas@...il.com,
 yaoxt.fnst@...itsu.com, peterz@...radead.org, gregkh@...uxfoundation.org,
 quic_jjohnson@...cinc.com, ilpo.jarvinen@...ux.intel.com,
 bhelgaas@...gle.com, andriy.shevchenko@...ux.intel.com,
 mika.westerberg@...ux.intel.com, akpm@...ux-foundation.org,
 gourry@...rry.net, linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 nvdimm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
 linux-pm@...r.kernel.org, rrichter@....com, benjamin.cheatham@....com,
 PradeepVineshReddy.Kodamati@....com, lizhijian@...itsu.com
Subject: Re: [PATCH v3 1/4] kernel/resource: Provide mem region release for
 SOFT RESERVES

On 4/4/2025 8:16 AM, Jonathan Cameron wrote:
> On Thu, 3 Apr 2025 13:33:12 -0500
> Terry Bowman <terry.bowman@....com> wrote:
> 
>> From: Nathan Fontenot <nathan.fontenot@....com>
>>
>> Add a release_Sam_region_adjustable() interface to allow for
> 
> Who is Sam?  (typo)
> 

Hi Jonathan,

It is a typo. I will fix.

>> removing SOFT RESERVE memory resources. This extracts out the code
>> to remove a mem region into a common __release_mem_region_adjustable()
>> routine, this routine takes additional parameters of an IORES
>> descriptor type to add checks for IORES_DESC_* and a flag to check
>> for IORESOURCE_BUSY to control it's behavior.
>>
>> The existing release_mem_region_adjustable() is a front end to the
>> common code and a new release_srmem_region_adjustable() is added to
>> release SOFT RESERVE resources.
>>
>> Signed-off-by: Nathan Fontenot <nathan.fontenot@....com>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> ---
>>  include/linux/ioport.h |  3 +++
>>  kernel/resource.c      | 55 +++++++++++++++++++++++++++++++++++++++---
>>  2 files changed, 54 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>> index 5385349f0b8a..718360c9c724 100644
>> --- a/include/linux/ioport.h
>> +++ b/include/linux/ioport.h
>> @@ -357,6 +357,9 @@ extern void __release_region(struct resource *, resource_size_t,
>>  #ifdef CONFIG_MEMORY_HOTREMOVE
>>  extern void release_mem_region_adjustable(resource_size_t, resource_size_t);
>>  #endif
>> +#ifdef CONFIG_CXL_REGION
>> +extern void release_srmem_region_adjustable(resource_size_t, resource_size_t);
> I'm not sure the srmem is obvious enough.  Maybe it's worth the long
> name to spell it out some more.. e.g. something like
> 

Yes, I'll update with a re name.

> extern void release_softresv_mem_region_adjustable() ?
>> +#endif
>>  #ifdef CONFIG_MEMORY_HOTPLUG
>>  extern void merge_system_ram_resource(struct resource *res);
>>  #endif
>> diff --git a/kernel/resource.c b/kernel/resource.c
>> index 12004452d999..0195b31064b0 100644
>> --- a/kernel/resource.c
>> +++ b/kernel/resource.c
>> @@ -1387,7 +1387,7 @@ void __release_region(struct resource *parent, resource_size_t start,
>>  }
>>  EXPORT_SYMBOL(__release_region);
>>  
>> -#ifdef CONFIG_MEMORY_HOTREMOVE
>> +#if defined(CONFIG_MEMORY_HOTREMOVE) || defined(CONFIG_CXL_REGION)
>>  /**
>>   * release_mem_region_adjustable - release a previously reserved memory region
> 
> Looks like you left the old docs which I'm guessing is not the intent.
> 

Correct, this is not intended. Ill remove.

>>   * @start: resource start address
>> @@ -1407,7 +1407,10 @@ EXPORT_SYMBOL(__release_region);
>>   *   assumes that all children remain in the lower address entry for
>>   *   simplicity.  Enhance this logic when necessary.
>>   */
>> -void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>> +static void __release_mem_region_adjustable(resource_size_t start,
>> +					    resource_size_t size,
>> +					    bool busy_check,
>> +					    int res_desc)
>>  {
>>  	struct resource *parent = &iomem_resource;
>>  	struct resource *new_res = NULL;
>> @@ -1446,7 +1449,12 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>>  		if (!(res->flags & IORESOURCE_MEM))
>>  			break;
>>  
>> -		if (!(res->flags & IORESOURCE_BUSY)) {
>> +		if (busy_check && !(res->flags & IORESOURCE_BUSY)) {
>> +			p = &res->child;
>> +			continue;
>> +		}
>> +
>> +		if (res_desc != IORES_DESC_NONE && res->desc != res_desc) {
>>  			p = &res->child;
>>  			continue;
>>  		}
>> @@ -1496,7 +1504,46 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>>  	write_unlock(&resource_lock);
>>  	free_resource(new_res);
>>  }
>> -#endif	/* CONFIG_MEMORY_HOTREMOVE */
>> +#endif
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/**
>> + * release_mem_region_adjustable - release a previously reserved memory region
> As above. I was surprised to see new docs in here for an existing function.
> I think you forgot to delete the now wrongly placed ones above.
> 
> Jonathan
> 
Right, I'll remove the now old function comment.

-Terry