Re: [PATCH v2 1/2] arm64: ptdump: Make note_page_flush() range aware

Hi Will,

On Fri, Aug 07, 2026 at 12:46:43PM +0100, Will Deacon wrote:
> On Fri, Jul 24, 2026 at 07:54:30PM +0100, Wei-Lin Chang wrote:
> > note_page_flush() calls note_page() with addr == 0 and level == -1 to
> > dump the last row of a ptdump. addr == 0 (1 << 64 wrapped around)
> > renders a huge region with enormous size for address spaces with
> > IA bits < 64. For example the stage-2 page tables and the EFI runtime
> > page table.
> > 
> > More importantly, the last region of the address space and everything
> > after the address space up to 1 << 64 are merged into one row of
> > output. If the last region within the address space is valid, it will
> > appear to remain valid up to 1 << 64 with the same attributes.
> > 
> > Currently only the EFI runtime ptdump is affected by this, but KVM will
> > soon fix its stage-2 ptdump by using note_page_flush(). Here is an
> > example of an EFI runtime ptdump (last row):
> > 
> > 0x0000008000000000-0x0000000000000000   17179868672G PGD
> > 
> > With this patch:
> > 
> > 0x0000008000000000-0x0001000000000000      261632G PGD
> > 
> > To fix this, use ptdump_state.range[] to figure out where the address
> > space ends, and call note_page() with that.
> > 
> > Fixes: 9d80448ac92b ("efi/arm64: Add debugfs node to dump UEFI runtime page tables")
> > Signed-off-by: Wei-Lin Chang <[email protected]>
> > ---
> >  arch/arm64/mm/ptdump.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> > index 1c20144700d7..5b34060ceb96 100644
> > --- a/arch/arm64/mm/ptdump.c
> > +++ b/arch/arm64/mm/ptdump.c
> > @@ -278,9 +278,24 @@ void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
> >  
> >  void note_page_flush(struct ptdump_state *pt_st)
> >  {
> > +	const struct ptdump_range *range = pt_st->range;
> > +	unsigned long end = 0;
> >  	pte_t pte_zero = {0};
> >  
> > -	note_page(pt_st, 0, -1, pte_val(pte_zero));
> > +	while (range->start != range->end) {
> > +		end = range->end;
> > +		range++;
> > +	}
> 
> This seems to be duplicating some of what the core code does already in
> ptdump_walk_pgd(). Can we retrieve the information we need from the
> containing 'struct ptdump_pg_state' structure instead of recomputing
> the address?

I can add a member end_address in ptdump_pg_state, and initialize it
with the last range->end when users initialize ptdump_pg_state
(ptdump_walk() and ptdump_check_wx()). Is that what you had in mind?

Thanks,
Wei-Lin Chang

> 
> Will