linux-kernel - Re: [PATCH v2 6/7] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY

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Date:   Mon, 1 Mar 2021 11:07:38 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>, VlastimilBabkavbabka@...e.cz,
        pasha.tatashin@...een.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v2 6/7] x86/Kconfig: Introduce
 ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE

On Mon, Mar 01, 2021 at 09:45:07AM +0100, David Hildenbrand wrote:
> Take your config and set
> 	X86_5LEVEL=n
> (because it enforces SPARSEMEM_VMEMMAP)
> and
> 	SPARSEMEM_VMEMMAP=n
> 
> When compiling, you'll end up with a config like
> 	CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> 	# CONFIG_SPARSEMEM_VMEMMAP is not set

I see

> 
> Yet, with your patch you would get
> 
> ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE=y
> 
> And it would not get fenced off in the code, right?
> 
> 
> I think you either have to check (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) in
> addition in your code, or enforce it differently. Like
> 
> 
> config MHP_MEMMAP_ON_MEMORY
> 	depends on SPARSEMEM_VMEMMAP && ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
> 	bool
> 
> 
> Then you can simplify the arch Kconfig settings, removing the sparesemem
> dependency there.

Yes, will do it this way.

Thanks!

-- 
Oscar Salvador
SUSE L3