linux-kernel - Re: [PATCH] arm64/mm: Re-organize arch_make_huge

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Message-ID: <1a724b58-d61b-443d-9f3d-aebcd35e9610@arm.com>
Date: Mon, 4 Nov 2024 10:28:35 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Catalin Marinas <catalin.marinas@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
 Ryan Roberts <ryan.roberts@....com>, Mark Rutland <mark.rutland@....com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/mm: Re-organize arch_make_huge_pte()



On 11/1/24 23:05, Catalin Marinas wrote:
> On Tue, 29 Oct 2024 10:15:29 +0530, Anshuman Khandual wrote:
>> Core HugeTLB defines a fallback definition for arch_make_huge_pte(), which
>> calls platform provided pte_mkhuge(). But if any platform already provides
>> an override for arch_make_huge_pte(), then it does not need to provide the
>> helper pte_mkhuge().
>>
>> arm64 override for arch_make_huge_pte() calls pte_mkhuge() internally, thus
>> creating an impression, that both of these callbacks are being used in core
>> HugeTLB and hence required to be defined. This drops off pte_mkhuge() which
>> was never required to begin with as there could not be any section mappings
>> at the PTE level. Re-organize arch_make_huge_pte() based on requested page
>> size and create the entry for the applicable page table level as needed. It
>> also removes a redundancy of clearing PTE_TABLE_BIT bit followed by setting
>> both PTE_TABLE_BIT and PTE_VALID bits (via PTE_TYPE_MASK) in the pte, while
>> creating CONT_PTE_SIZE size entries.
>>
>> [...]
> 
> Applied to arm64 (for-next/misc), thanks!
> 
> [1/1] arm64/mm: Re-organize arch_make_huge_pte()
>       https://git.kernel.org/arm64/c/f8192813dcbe
> 
> I think we can now get pte_mkcont() to only set PTE_CONT without
> touching PTE_TYPE_PAGE. Previously it wasn't possible because
> pte_mkhuge() was clearing the PTE_TABLE_BIT and we added it back via
> pte_mkcont(). Give it a try and send an additional patch cleaning up
> pte_mkcont() if this works. Thanks.

Yes, it does indeed work. Sent the following patch for the same.

https://lore.kernel.org/all/20241104041617.3804617-1-anshuman.khandual@arm.com/