linux-kernel - Re: [PATCH v14 21/22] arm64: mm: Convert mm/dump.c to use walk_page

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Date:   Wed, 30 Oct 2019 16:45:35 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Steven Price <steven.price@....com>
Cc:     linux-mm@...ck.org, Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v14 21/22] arm64: mm: Convert mm/dump.c to use
 walk_page_range()

On Mon, Oct 28, 2019 at 01:59:09PM +0000, Steven Price wrote:
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 93f9f77582ae..9d9b740a86d2 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -15,6 +15,7 @@
>  #include <linux/io.h>
>  #include <linux/init.h>
>  #include <linux/mm.h>
> +#include <linux/ptdump.h>
>  #include <linux/sched.h>
>  #include <linux/seq_file.h>
>  
> @@ -75,10 +76,11 @@ static struct addr_marker address_markers[] = {
>   * dumps out a description of the range.
>   */
>  struct pg_state {
> +	struct ptdump_state ptdump;
>  	struct seq_file *seq;
>  	const struct addr_marker *marker;
>  	unsigned long start_address;
> -	unsigned level;
> +	int level;
>  	u64 current_prot;
>  	bool check_wx;
>  	unsigned long wx_pages;
> @@ -178,6 +180,10 @@ static struct pg_level pg_level[] = {
>  		.name	= "PGD",
>  		.bits	= pte_bits,
>  		.num	= ARRAY_SIZE(pte_bits),
> +	}, { /* p4d */
> +		.name	= "P4D",
> +		.bits	= pte_bits,
> +		.num	= ARRAY_SIZE(pte_bits),
>  	}, { /* pud */
>  		.name	= (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
>  		.bits	= pte_bits,

We could use "PGD" for the p4d entry since we don't have five levels.
This patches the "PGD" name used for pud/pmd when these levels are
folded.

> @@ -240,11 +246,15 @@ static void note_prot_wx(struct pg_state *st, unsigned long addr)
>  	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
>  }
>  
> -static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> -				u64 val)
> +static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> +		      unsigned long val)
>  {
> +	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
>  	static const char units[] = "KMGTPE";
> -	u64 prot = val & pg_level[level].mask;
> +	u64 prot = 0;
> +
> +	if (level >= 0)
> +		prot = val & pg_level[level].mask;

I think this test is not needed as we never have level < 0. The only
call with a level 0 is from ptdump_hole() where the level passed is
depth+1 while depth is -1 or higher.

Anyway, we can keep this test _if_ we shift the levels down. I find it
quite confusing that ptdump_hole() takes a 'depth' argument where 0 is
PGD and 4 is PTE while for note_page() 1 is PGD and 5 PTE.

-- 
Catalin