linux-kernel - Re: [PATCH v1 4/5] mm: ptdump: Support hugepd table entries

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Message-ID: <87zgxzyvn3.fsf@dja-thinkpad.axtens.net>
Date:   Fri, 16 Apr 2021 09:29:20 +1000
From:   Daniel Axtens <dja@...ens.net>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Steven Price <steven.price@....com>, akpm@...ux-foundation.org
Cc:     linux-arch@...r.kernel.org, linux-s390@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 4/5] mm: ptdump: Support hugepd table entries

Hi Christophe,

> Which hugepd, page table entries can be at any level
> and can be of any size.
>
> Add support for them.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  mm/ptdump.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/mm/ptdump.c b/mm/ptdump.c
> index 61cd16afb1c8..6efdb8c15a7d 100644
> --- a/mm/ptdump.c
> +++ b/mm/ptdump.c
> @@ -112,11 +112,24 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
>  {
>  	struct ptdump_state *st = walk->private;
>  	pte_t val = ptep_get(pte);
> +	unsigned long page_size = next - addr;
> +	int level;
> +
> +	if (page_size >= PGDIR_SIZE)
> +		level = 0;
> +	else if (page_size >= P4D_SIZE)
> +		level = 1;
> +	else if (page_size >= PUD_SIZE)
> +		level = 2;
> +	else if (page_size >= PMD_SIZE)
> +		level = 3;
> +	else
> +		level = 4;
>  
>  	if (st->effective_prot)
> -		st->effective_prot(st, 4, pte_val(val));
> +		st->effective_prot(st, level, pte_val(val));
>  
> -	st->note_page(st, addr, 4, pte_val(val), PAGE_SIZE);
> +	st->note_page(st, addr, level, pte_val(val), page_size);

It seems to me that passing both level and page_size is a bit redundant,
but I guess it does reduce the impact on each arch's code?

Kind regards,
Daniel

>  
>  	return 0;
>  }
> -- 
> 2.25.0