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Wed, 29 Jul 2026 12:37:00 +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 +/ToAOzzaWpxRgAAD6G6ig (envelope-from ); Wed, 29 Jul 2026 12:37:00 +0000 Date: Wed, 29 Jul 2026 13:36:58 +0100 From: Pedro Falcato To: Muhammad Usama Anjum Cc: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Dimitri Sivanich , Arnd Bergmann , Greg Kroah-Hartman , "James E.J. Bottomley" , Helge Deller , Juergen Gross , Stefano Stabellini , Muchun Song , Oscar Salvador , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Andrey Ryabinin , David Hildenbrand , Pasha Tatashin , Chris Li , Kairui Song , Uladzislau Rezki , Steven Rostedt , Masami Hiramatsu , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , SJ Park , "Matthew Wilcox (Oracle)" , Jan Kara , Jason Gunthorpe , Leon Romanovsky , Miaohe Lin , Dennis Zhou , Tejun Heo , Christoph Lameter , Mike Rapoport , Johannes Weiner , ziy@nvidia.com, agordeev@linux.ibm.com, ryan.roberts@arm.com, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-parisc@vger.kernel.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev Subject: Re: [PATCH RFC 09/11] misc/sgi-gru: use ptep_get() for page-table reads Message-ID: References: <20260727164715.2866609-1-usama.anjum@arm.com> <20260727164715.2866609-10-usama.anjum@arm.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260727164715.2866609-10-usama.anjum@arm.com> X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_GT_50(0.00)[66]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux.intel.com,intel.com,ursulin.net,gmail.com,ffwll.ch,hpe.com,arndb.de,linuxfoundation.org,hansenpartnership.com,gmx.de,suse.com,kernel.org,linux.dev,suse.de,linux-foundation.org,infradead.org,soleen.com,tencent.com,goodmis.org,iogearbox.net,redhat.com,suse.cz,ziepe.ca,huawei.com,gentwo.org,cmpxchg.org,nvidia.com,linux.ibm.com,arm.com,vger.kernel.org,lists.freedesktop.org,lists.xenproject.org,kvack.org,googlegroups.com,lists.linux.dev]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_SOME(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[arm.com:email,pedro-suse.lan:mid,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Score: -2.80 X-Spam-Level: On Mon, Jul 27, 2026 at 05:47:00PM +0100, Muhammad Usama Anjum wrote: > A leaf PMD is being read through ptep_get() by treating the PMD address > as PTE-sized table storage. ptep_get() now accepts hw_pte_t *, so update > the cast accordingly. > > pte_offset_kernel() also returns hw_pte_t *. Get pte_t value by calling > ptep_get(). > > Signed-off-by: Muhammad Usama Anjum > --- > drivers/misc/sgi-gru/grufault.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c > index 3557d78ee47a2..ff89d34ad2aa4 100644 > --- a/drivers/misc/sgi-gru/grufault.c > +++ b/drivers/misc/sgi-gru/grufault.c > @@ -228,10 +228,10 @@ static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr, > goto err; > #ifdef CONFIG_X86_64 > if (unlikely(pmd_leaf(*pmdp))) > - pte = ptep_get((pte_t *)pmdp); > + pte = ptep_get((hw_pte_t *)pmdp); > else > #endif > - pte = *pte_offset_kernel(pmdp, vaddr); > + pte = ptep_get(pte_offset_kernel(pmdp, vaddr)); > > if (unlikely(!pte_present(pte) || > (write && (!pte_write(pte) || !pte_dirty(pte))))) This code is super, super broken. Can we remove this ASAP? For starters, we're using is_vm_hugetlb_page() to detect page shift, the code does not grab refs on the pages, uses pte_offset_kernel() on user page tables, does not handle PUD-level hugepages, does not handle PMD-level hugepages on !x86_64, does not hold page table locks nor check for pte table retraction, etc I don't think I need to go on. -- Pedro