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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 Cc: Andrew Morton , Jason Gunthorpe , Peter Xu , Michael Ellerman , Nicholas Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org 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-Rspamd-Queue-Id: A30974001D X-Stat-Signature: 83wj6u3r6cdpbxczzy463sdesqyb9tku X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1716610382-525429 X-HE-Meta: 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 /jU+V+TG HEybXywCMTDPlnaKg63tknDbQPUPNFjEQW8h1kWiiXsXk6vybx0Ksj8o9jOwG8MTPz2n0gXFr9izZoc7fLFgrXDeyIRK1SMd29rtl48avcxyw0LAD2qSYTMmmr7zUjsxFKqw6EPnwnt/daR1PdoTfb3YV8SYB4Sb5y+xzrCFpomiYdOSEZBAhvk3rj0GL+SCQOXY/cvLONq0IM2+CTMQBghX+0VwuybYIZ1IfmO0Okt7SVoTyjOR9l5RSOL0Prb9siM3pnGE3UrsfwnKqdz8pXxW0Dmv7li7oAHGi/A2afAk7pvETdtphquFAxg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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