linux-kernel - Re: [PATCH v7 3/6] arm64: ptdump: Use the mask from the state structure

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Message-ID: <Zpppu5DBmb7MLDXD@google.com>
Date: Fri, 19 Jul 2024 13:27:23 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: Will Deacon <will@...nel.org>
Cc: akpm@...ux-foundation.org, alexghiti@...osinc.com, ankita@...dia.com,
	ardb@...nel.org, catalin.marinas@....com,
	christophe.leroy@...roup.eu, james.morse@....com,
	vdonnefort@...gle.com, mark.rutland@....com, maz@...nel.org,
	oliver.upton@...ux.dev, rananta@...gle.com, ryan.roberts@....com,
	shahuang@...hat.com, suzuki.poulose@....com, yuzenghui@...wei.com,
	kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v7 3/6] arm64: ptdump: Use the mask from the state
 structure

On Fri, Jul 05, 2024 at 12:12:29PM +0100, Will Deacon wrote:
> On Fri, Jun 21, 2024 at 12:32:27PM +0000, Sebastian Ene wrote:
> > Printing the descriptor attributes requires accessing a mask which has a
> > different set of attributes for stage-2. In preparation for adding support
> > for the stage-2 pagetables dumping, use the mask from the local context
> > and not from the globally defined pg_level array. Store a pointer to
> > the pg_level array in the ptdump state structure. This will allow us to
> > extract the mask which is wrapped in the pg_level array and use it for
> > descriptor parsing in the note_page.
> > 
> > Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
> > ---
> >  arch/arm64/include/asm/ptdump.h |  1 +
> >  arch/arm64/mm/ptdump.c          | 13 ++++++++-----
> >  2 files changed, 9 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> > index c550b2afcab7..a4125d8d5a32 100644
> > --- a/arch/arm64/include/asm/ptdump.h
> > +++ b/arch/arm64/include/asm/ptdump.h
> > @@ -44,6 +44,7 @@ struct pg_level {
> >   */
> >  struct pg_state {
> >  	struct ptdump_state ptdump;
> > +	struct pg_level *pg_level;
> >  	struct seq_file *seq;
> >  	const struct addr_marker *marker;
> >  	const struct mm_struct *mm;
> > diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> > index e370b7a945de..9637a6415ea7 100644
> > --- a/arch/arm64/mm/ptdump.c
> > +++ b/arch/arm64/mm/ptdump.c
> > @@ -192,6 +192,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> >  	       u64 val)
> >  {
> >  	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
> > +	struct pg_level *pg_info = st->pg_level;
> >  	static const char units[] = "KMGTPE";
> >  	u64 prot = 0;
> >  
> > @@ -201,7 +202,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> >  		level = 0;
> >  
> >  	if (level >= 0)
> > -		prot = val & pg_level[level].mask;
> > +		prot = val & pg_info[level].mask;
> 
> If you rename the existing 'pg_level' array to something like
> 'kernel_pg_levels' then I think your local 'pg_info' variable can be
> called 'pg_level' and this line doesn't need to change.
> 

This is a good ideea, thanks. I applied your suggestion

> >  
> >  	if (st->level == -1) {
> >  		st->level = level;
> > @@ -227,10 +228,10 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> >  			unit++;
> >  		}
> >  		pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
> > -				   pg_level[st->level].name);
> > -		if (st->current_prot && pg_level[st->level].bits)
> > -			dump_prot(st, pg_level[st->level].bits,
> > -				  pg_level[st->level].num);
> > +				   pg_info[st->level].name);
> > +		if (st->current_prot && pg_info[st->level].bits)
> > +			dump_prot(st, pg_info[st->level].bits,
> > +				  pg_info[st->level].num);
> 
> I think this could then stay as-is too.
> 
> >  		pt_dump_seq_puts(st->seq, "\n");
> >  
> >  		if (addr >= st->marker[1].start_address) {
> > @@ -262,6 +263,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
> >  		.seq = s,
> >  		.marker = info->markers,
> >  		.mm = info->mm,
> > +		.pg_level = &pg_level[0],
> 
> Can't this just be '.pg_level = kernel_pg_levels'?
> 
> Will


Seb