linux-kernel - Re: [PATCH V2] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR

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Message-ID: <CAMj1kXGbJ4q1rchCbDp35rdWRyzuG-nZnQ2KgE46FtkPUg-+SQ@mail.gmail.com>
Date: Fri, 18 Apr 2025 09:01:40 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-arm-kernel@...ts.infradead.org, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Ryan Roberts <ryan.roberts@....com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] arm64/mm: Re-organise setting up FEAT_S1PIE registers
 PIRE0_EL1 and PIR_EL1

On Wed, 16 Apr 2025 at 05:56, Anshuman Khandual
<anshuman.khandual@....com> wrote:
>
> mov_q cannot really move PIE_E[0|1] macros into a general purpose register
> as expected if those macro constants contain some 128 bit layout elements,
> that are required for D128 page tables. The primary issue is that for D128,
> PIE_E[0|1] are defined in terms of 128-bit types with shifting and masking,
> which the assembler can't accommodate.
>
> Instead pre-calculate these PIRE0_EL1/PIR_EL1 constants into asm-offsets.h
> based PIE_E0_ASM/PIE_E1_ASM which can then be used in arch/arm64/mm/proc.S.
>
> While here also move PTE_MAYBE_NG/PTE_MAYBE_SHARED assembly overrides into
> arch/arm64/kernel/asm-offsets.c to ensure PIRE0_EL1/PIR_EL1 are calculated
> in assembly without arm64_use_ng_mappings and lpa2_is_enabled() symbols
> being accessible. Also move the corresponding comment as well.
>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This patch applies on v6.15-rc2
>
> Changes in V2:
>
> - Added asm-offsets.c based PIE_E0_ASM and PIE_E1_ASM symbols as per Ard
> - Moved PTE_MAYBE_NG and PTE_MAYBE_SHARED overrides inside asm-offsets.c
>   along with the corresponding comment as per Ard
>
> Changes in V1:
>
> https://lore.kernel.org/linux-arm-kernel/20250410074024.1545768-1-anshuman.khandual@arm.com/
>
>  arch/arm64/kernel/asm-offsets.c | 16 ++++++++++++++++
>  arch/arm64/mm/proc.S            | 19 ++-----------------
>  2 files changed, 18 insertions(+), 17 deletions(-)
>

Reviewed-by: Ard Biesheuvel <ardb@...nel.org>