linux-kernel - Re: [PATCH 1/6] dax/hmem, e820, resource: Defer Soft Reserved registration until hmem is ready

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Message-ID: <a72ffd72-3731-426b-a875-fc85e006a31b@amd.com>
Date: Mon, 29 Sep 2025 21:56:11 -0700
From: "Koralahalli Channabasappa, Smita" <skoralah@....com>
To: Borislav Petkov <bp@...en8.de>,
 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, Davidlohr Bueso <dave@...olabs.net>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Dave Jiang <dave.jiang@...el.com>,
 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>, 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 KH <gregkh@...uxfoundation.org>,
 Nathan Fontenot <nathan.fontenot@....com>,
 Terry Bowman <terry.bowman@....com>, Robert Richter <rrichter@....com>,
 Benjamin Cheatham <benjamin.cheatham@....com>,
 PradeepVineshReddy Kodamati <PradeepVineshReddy.Kodamati@....com>,
 Zhijian Li <lizhijian@...itsu.com>
Subject: Re: [PATCH 1/6] dax/hmem, e820, resource: Defer Soft Reserved
 registration until hmem is ready

Hi Boris,

On 9/9/2025 9:12 AM, Borislav Petkov wrote:
> On Fri, Aug 22, 2025 at 03:41:57AM +0000, Smita Koralahalli wrote:
>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
>> index c3acbd26408b..aef1ff2cabda 100644
>> --- a/arch/x86/kernel/e820.c
>> +++ b/arch/x86/kernel/e820.c
>> @@ -1153,7 +1153,7 @@ void __init e820__reserve_resources_late(void)
>>   	res = e820_res;
>>   	for (i = 0; i < e820_table->nr_entries; i++) {
>>   		if (!res->parent && res->end)
>> -			insert_resource_expand_to_fit(&iomem_resource, res);
>> +			insert_resource_late(res);
>>   		res++;
>>   	}
>>
> 
> Btw, this doesn't even build and cover letter doesn't say what it applies
> ontop so I applied it on my pile of tip/master.
> 
> kernel/resource.c: In function ‘region_intersects_soft_reserve’:
> kernel/resource.c:694:36: error: ‘soft_reserve_resource’ undeclared (first use in this function); did you mean ‘devm_release_resource’?
>    694 |         ret = __region_intersects(&soft_reserve_resource, start, size, flags,
>        |                                    ^~~~~~~~~~~~~~~~~~~~~
>        |                                    devm_release_resource
> kernel/resource.c:694:36: note: each undeclared identifier is reported only once for each function it appears in
> make[3]: *** [scripts/Makefile.build:287: kernel/resource.o] Error 1
> make[2]: *** [scripts/Makefile.build:556: kernel] Error 2
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [/mnt/kernel/kernel/2nd/linux/Makefile:2011: .] Error 2
> make: *** [Makefile:248: __sub-make] Error 2

Apologies for the delay.

This was based on mainline. I have rebased the series onto the latest 
mainline and sent out a new revision and noted it in the cover letter.

https://lore.kernel.org/all/20250930044757.214798-2-Smita.KoralahalliChannabasappa@amd.com/

> 
> Also, I'd do this resource insertion a bit differently:
> 
> insert_resource_expand_to_fit(struct resource *new)
> {
> 	struct resource *root = &iomem_resource;
> 
> 	if (new->desc == IORES_DESC_SOFT_RESERVED)
> 		root = &soft_reserve_resource;
> 
> 	return __insert_resource_expand_to_fit(root, new);
> }
> 
> and rename the current insert_resource_expand_to_fit() to the __ variant.

I have made these changes as well.

Thanks
Smita

> 
> It looks like you want to intercept all callers of
> insert_resource_expand_to_fit() instead of defining a separate set which works
> on the soft-reserve thing.
> 
> Oh well, the resource code is yucky already.
>