Re: [PATCH v14 21/22] arm64: mm: Convert mm/dump.c to use walk_page_range()

From: Catalin Marinas <catalin.marinas@arm.com>
To: Steven Price <steven.price@arm.com>
Cc: linux-mm@kvack.org, "Andy Lutomirski" <luto@kernel.org>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Arnd Bergmann" <arnd@arndb.de>, "Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"James Morse" <james.morse@arm.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Will Deacon" <will@kernel.org>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	"Mark Rutland" <Mark.Rutland@arm.com>,
	"Liang, Kan" <kan.liang@linux.intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [PATCH v14 21/22] arm64: mm: Convert mm/dump.c to use walk_page_range()
Date: Wed, 30 Oct 2019 16:45:35 +0000	[thread overview]
Message-ID: <20191030164535.GC13309@arrakis.emea.arm.com> (raw)
In-Reply-To: <20191028135910.33253-22-steven.price@arm.com>

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