linux-kernel - Re: [PATCH 0/5] arm64/mm: Drop PXD_TABLE

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Message-ID: <0ef88192-2523-418f-8ab7-442766a1c444@arm.com>
Date: Wed, 9 Oct 2024 14:32:05 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
 James Morse <james.morse@....com>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Ard Biesheuvel <ardb@...nel.org>, Mark Rutland <mark.rutland@....com>,
 kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] arm64/mm: Drop PXD_TABLE_BIT

On 05/10/2024 13:38, Anshuman Khandual wrote:
> Clearing PXD_TABLE_BIT i.e bit[1] on a page table entry always operates on
> the assumption that subsequent PXD_VALID i.e bit[0] is set. That's because
> bits[1:0]="01" makes a block mapping. So it is prudent to treat bits[1:0]
> as a single register field, which should be updated as block or table etc.
> Although mk_[pmd|pud]_sect_prot() helpers go to some extent in using these
> PXD_TYPE_SECT macros, their usage is not really consistent else where.
> 
> This series removes these table bit clearing for block mapping creation and
> eventually completely drops off those table macros.

Given the issue I just noticed in patch 2, I'm not sure if it's going to be
practical to remove the table bit after all? Sorry I didn't spot this before.

> 
> This series applies on v6.12-rc1.
> 
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Oliver Upton <oliver.upton@...ux.dev>
> Cc: James Morse <james.morse@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: kvmarm@...ts.linux.dev
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> 
> Anshuman Khandual (5):
>   arm64/mm: Drop pte_mkhuge()
>   arm64/mm: Replace PXD_TABLE_BIT with PXD_TYPE_[MASK|SECT]
>   arm64/ptdump: Test PMD_TYPE_MASK for block mapping
>   KVM: arm64: ptdump: Test PMD_TYPE_MASK for block mapping
>   arm64/mm: Drop PXD_TABLE_BIT
> 
>  arch/arm64/include/asm/pgtable-hwdef.h |  6 +-----
>  arch/arm64/include/asm/pgtable.h       | 20 ++++++++------------
>  arch/arm64/kvm/ptdump.c                |  4 ++--
>  arch/arm64/mm/hugetlbpage.c            |  2 +-
>  arch/arm64/mm/ptdump.c                 |  8 ++++----
>  5 files changed, 16 insertions(+), 24 deletions(-)
>