linux-kernel - Re: [PATCH 2/4] mm: pgalloc: support address-conditional pmd allocation

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Message-ID: <cf5409c3-254a-459b-8969-429db2ec6439@redhat.com>
Date: Wed, 21 Feb 2024 10:27:06 +0100
From: David Hildenbrand <david@...hat.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
 Maxwell Bland <mbland@...orola.com>,
 "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
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Subject: Re: [PATCH 2/4] mm: pgalloc: support address-conditional pmd
 allocation

On 21.02.24 08:13, Christophe Leroy wrote:
> 
> 
> Le 20/02/2024 à 21:32, Maxwell Bland a écrit :
>> [Vous ne recevez pas souvent de courriers de mbland@...orola.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>>
>> While other descriptors (e.g. pud) allow allocations conditional on
>> which virtual address is allocated, pmd descriptor allocations do not.
>> However, adding support for this is straightforward and is beneficial to
>> future kernel development targeting the PMD memory granularity.
>>
>> As many architectures already implement pmd_populate_kernel in an
>> address-generic manner, it is necessary to roll out support
>> incrementally. For this purpose a preprocessor flag,
> 
> Is it really worth it ? It is only 48 call sites that need to be
> updated. It would avoid that processor flag and avoid introducing that
> pmd_populate_kernel_at() in kernel core.

+1, let's avoid that if possible.

-- 
Cheers,

David / dhildenb