linux-kernel - Re: [PATCHv7 07/16] x86/mm: Return correct level from lookup

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Message-ID: <zhbhgq27kjrhkdgbxomjykjez2i4hckguvmxyptvfvoftue5ca@zowl5qbl6psl>
Date: Mon, 19 Feb 2024 15:52:41 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Baoquan He <bhe@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, Elena Reshetova <elena.reshetova@...el.com>, 
	Jun Nakajima <jun.nakajima@...el.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Tom Lendacky <thomas.lendacky@....com>, "Kalra, Ashish" <ashish.kalra@....com>, 
	Sean Christopherson <seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>, kexec@...ts.infradead.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv7 07/16] x86/mm: Return correct level from
 lookup_address() if pte is none

On Mon, Feb 19, 2024 at 01:12:32PM +0800, Baoquan He wrote:
> On 02/12/24 at 12:44pm, Kirill A. Shutemov wrote:
> > lookup_address() only returns correct page table level for the entry if
> > the entry is not none.
> > 
> > Make the helper to always return correct 'level'. It allows to implement
> > iterator over kernel page tables using lookup_address().
> > 
> > Add one more entry into enum pg_level to indicate size of VA covered by
> > one PGD entry in 5-level paging mode.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> > ---
> >  arch/x86/include/asm/pgtable_types.h | 1 +
> >  arch/x86/mm/pat/set_memory.c         | 8 ++++----
> >  2 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> > index 0b748ee16b3d..3f648ffdfbe5 100644
> > --- a/arch/x86/include/asm/pgtable_types.h
> > +++ b/arch/x86/include/asm/pgtable_types.h
> > @@ -548,6 +548,7 @@ enum pg_level {
> >  	PG_LEVEL_2M,
> >  	PG_LEVEL_1G,
> >  	PG_LEVEL_512G,
> > +	PG_LEVEL_256T,
> >  	PG_LEVEL_NUM
> >  };
> >  
> > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> > index f92da8c9a86d..3612e3167147 100644
> > --- a/arch/x86/mm/pat/set_memory.c
> > +++ b/arch/x86/mm/pat/set_memory.c
> > @@ -666,32 +666,32 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
> 
> LGTM,
> 
> Reviewed-by: Baoquan He <bhe@...hat.com>
> 
> By the way, we may need update the code comment above function
> lookup_address_in_pgd() and function lookup_address() since they don't
> reflect the latest behaviour of them.

I am not sure what part of the comment you see doesn't reflect the
behaviour. From my PoV, changed code matches the comment closer that
original.

Hm?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov