linux-kernel - Re: [PATCH 2/2] arm64/ptdump: Replace u64 with pteval

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Message-ID: <16c12c3f-f2c2-45fa-9db6-4dfaeb002059@arm.com>
Date: Mon, 17 Mar 2025 09:28:48 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Steven Price <steven.price@....com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Nicholas Piggin <npiggin@...il.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
 linux-s390@...r.kernel.org, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH 2/2] arm64/ptdump: Replace u64 with pteval_t

On 17/03/2025 06:18, Anshuman Khandual wrote:
> Page table entry's value, mask and protection are represented with pteval_t
> data type format not u64 that has been assumed while dumping the page table
> entries. Replace all such u64 instances with pteval_t instead as required.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  arch/arm64/include/asm/ptdump.h | 8 ++++----
>  arch/arm64/mm/ptdump.c          | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index e5da9ce8a515..476a870489b9 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -24,8 +24,8 @@ struct ptdump_info {
>  };
>  
>  struct ptdump_prot_bits {
> -	u64		mask;
> -	u64		val;
> +	pteval_t	mask;
> +	pteval_t	val;

Given Ard's suggestion of using "ptdesc" as a generic term for PTDESC_SHIFT (or
PTDESC_ORDER, or whatever we ended up calling it), I wonder if it would be
cleaner to do the same with the types? We could have a ptdesc_t, which is
typedef'ed as u64 (or u128), then pteval_t, pmdval_t, ..., could all be
typedef'ed as ptdesc_t. Then for code that just wants a generic pgtable
descriptor value, we can use that type to indicate that it can be at any level.

Thanks,
Ryan

>  	const char	*set;
>  	const char	*clear;
>  };
> @@ -34,7 +34,7 @@ struct ptdump_pg_level {
>  	const struct ptdump_prot_bits *bits;
>  	char name[4];
>  	int num;
> -	u64 mask;
> +	pteval_t mask;
>  };
>  
>  /*
> @@ -51,7 +51,7 @@ struct ptdump_pg_state {
>  	const struct mm_struct *mm;
>  	unsigned long start_address;
>  	int level;
> -	u64 current_prot;
> +	pteval_t current_prot;
>  	bool check_wx;
>  	unsigned long wx_pages;
>  	unsigned long uxn_pages;
> diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> index fd1610b4fd15..a5651be95868 100644
> --- a/arch/arm64/mm/ptdump.c
> +++ b/arch/arm64/mm/ptdump.c
> @@ -194,7 +194,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
>  	struct ptdump_pg_state *st = container_of(pt_st, struct ptdump_pg_state, ptdump);
>  	struct ptdump_pg_level *pg_level = st->pg_level;
>  	static const char units[] = "KMGTPE";
> -	u64 prot = 0;
> +	pteval_t prot = 0;
>  
>  	/* check if the current level has been folded dynamically */
>  	if (st->mm && ((level == 1 && mm_p4d_folded(st->mm)) ||