linux-kernel - Re: [PATCH v2 07/13] powerpc: add support for folded p4d page tables

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Message-ID: <20200219132420.GA5559@hump>
Date:   Wed, 19 Feb 2020 14:24:20 +0100
From:   Mike Rapoport <rppt@...nel.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Brian Cain <bcain@...eaurora.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Guan Xuetao <gxt@....edu.cn>,
        James Morse <james.morse@....com>,
        Jonas Bonn <jonas@...thpole.se>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Marc Zyngier <maz@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Rich Felker <dalias@...c.org>,
        Russell King <linux@...linux.org.uk>,
        Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Tony Luck <tony.luck@...el.com>, Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        kvmarm@...ts.cs.columbia.edu, kvm-ppc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-sh@...r.kernel.org, nios2-dev@...ts.rocketboards.org,
        openrisc@...ts.librecores.org,
        uclinux-h8-devel@...ts.sourceforge.jp,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH v2 07/13] powerpc: add support for folded p4d page tables

On Wed, Feb 19, 2020 at 01:07:55PM +0100, Christophe Leroy wrote:
> 
> Le 16/02/2020 à 09:18, Mike Rapoport a écrit :
> > diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> > index 206156255247..7bd4b81d5b5d 100644
> > --- a/arch/powerpc/mm/ptdump/ptdump.c
> > +++ b/arch/powerpc/mm/ptdump/ptdump.c
> > @@ -277,9 +277,9 @@ static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
> >   	}
> >   }
> > -static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
> > +static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start)
> >   {
> > -	pud_t *pud = pud_offset(pgd, 0);
> > +	pud_t *pud = pud_offset(p4d, 0);
> >   	unsigned long addr;
> >   	unsigned int i;
> > @@ -293,6 +293,22 @@ static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
> >   	}
> >   }
> > +static void walk_p4d(struct pg_state *st, pgd_t *pgd, unsigned long start)
> > +{
> > +	p4d_t *p4d = p4d_offset(pgd, 0);
> > +	unsigned long addr;
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < PTRS_PER_P4D; i++, p4d++) {
> > +		addr = start + i * P4D_SIZE;
> > +		if (!p4d_none(*p4d) && !p4d_is_leaf(*p4d))
> > +			/* p4d exists */
> > +			walk_pud(st, p4d, addr);
> > +		else
> > +			note_page(st, addr, 2, p4d_val(*p4d));
> 
> Level 2 is already used by walk_pud().
> 
> I think you have to increment the level used in walk_pud() and walk_pmd()
> and walk_pte()

Thanks for catching this!
I'll fix the numbers in the next version.
 
> > +	}
> > +}
> > +
> >   static void walk_pagetables(struct pg_state *st)
> >   {
> >   	unsigned int i;
> > @@ -306,7 +322,7 @@ static void walk_pagetables(struct pg_state *st)
> >   	for (i = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
> >   		if (!pgd_none(*pgd) && !pgd_is_leaf(*pgd))
> >   			/* pgd exists */
> > -			walk_pud(st, pgd, addr);
> > +			walk_p4d(st, pgd, addr);
> >   		else
> >   			note_page(st, addr, 1, pgd_val(*pgd));
> >   	}
> 
> Christophe

-- 
Sincerely yours,
Mike.