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Sat, 25 May 2024 04:13:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id o9+tEExlUWZ8BQAAD6G6ig (envelope-from ); Sat, 25 May 2024 04:13:00 +0000 Date: Sat, 25 May 2024 06:12:54 +0200 From: Oscar Salvador To: Christophe Leroy Subject: Re: [RFC PATCH v2 10/20] powerpc/mm: Fix __find_linux_pte() on 32 bits with PMD leaf entries Message-ID: References: <41bf05806501c0091a7d52e118b187416d24a76f.1715971869.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41bf05806501c0091a7d52e118b187416d24a76f.1715971869.git.christophe.leroy@csgroup.eu> X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_SEVEN(0.00)[9]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux-foundation.org,nvidia.com,redhat.com,ellerman.id.au,gmail.com,vger.kernel.org,kvack.org,lists.ozlabs.org]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[] X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Nicholas Piggin , linux-mm@kvack.org, Peter Xu , Jason Gunthorpe , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, May 17, 2024 at 09:00:04PM +0200, Christophe Leroy wrote: > Building on 32 bits with pmd_leaf() not returning always false leads > to the following error: I am curious though. pmd_leaf is only defined in include/linux/pgtable.h for 32bits, and is hardcoded to false. I do not see where we change it in previous patches, so is this artificial? > > CC arch/powerpc/mm/pgtable.o > arch/powerpc/mm/pgtable.c: In function '__find_linux_pte': > arch/powerpc/mm/pgtable.c:506:1: error: function may return address of local variable [-Werror=return-local-addr] > 506 | } > | ^ > arch/powerpc/mm/pgtable.c:394:15: note: declared here > 394 | pud_t pud, *pudp; > | ^~~ > arch/powerpc/mm/pgtable.c:394:15: note: declared here > > This is due to pmd_offset() being a no-op in that case. This is because 32bits powerpc include pgtable-nopmd.h? > So rework it for powerpc/32 so that pXd_offset() are used on real > pointers and not on on-stack copies. > > Signed-off-by: Christophe Leroy > --- > arch/powerpc/mm/pgtable.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c > index 59f0d7706d2f..51ee508eeb5b 100644 > --- a/arch/powerpc/mm/pgtable.c > +++ b/arch/powerpc/mm/pgtable.c > @@ -390,8 +390,12 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, > bool *is_thp, unsigned *hpage_shift) > { > pgd_t *pgdp; > - p4d_t p4d, *p4dp; > - pud_t pud, *pudp; > + p4d_t *p4dp; > + pud_t *pudp; > +#ifdef CONFIG_PPC64 > + p4d_t p4d; > + pud_t pud; > +#endif > pmd_t pmd, *pmdp; > pte_t *ret_pte; > hugepd_t *hpdp = NULL; > @@ -412,6 +416,7 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, > */ > pgdp = pgdir + pgd_index(ea); > p4dp = p4d_offset(pgdp, ea); > +#ifdef CONFIG_PPC64 > p4d = READ_ONCE(*p4dp); > pdshift = P4D_SHIFT; > > @@ -452,6 +457,11 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, > > pdshift = PMD_SHIFT; > pmdp = pmd_offset(&pud, ea); > +#else > + p4dp = p4d_offset(pgdp, ea); > + pudp = pud_offset(p4dp, ea); > + pmdp = pmd_offset(pudp, ea); I would drop a comment on top explaining that these are no-op for 32bits, otherwise it might not be obvious to people as why this distiction between 64 and 32bits. Other than that looks good to me -- Oscar Salvador SUSE Labs