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[2003:cb:c734:b800:12c4:65cd:348a:aee6]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-43947bdc5c4sm26951255e9.23.2025.02.10.11.38.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Feb 2025 11:38:48 -0800 (PST) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, nouveau@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev, David Hildenbrand , Andrew Morton , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Jonathan Corbet , Alex Shi , Yanteng Si , Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , SeongJae Park , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pasha Tatashin , Peter Xu , Alistair Popple , Jason Gunthorpe Subject: [PATCH v2 12/17] mm/rmap: handle device-exclusive entries correctly in page_vma_mkclean_one() Date: Mon, 10 Feb 2025 20:37:54 +0100 Message-ID: <20250210193801.781278-13-david@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250210193801.781278-1-david@redhat.com> References: <20250210193801.781278-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Ever since commit b756a3b5e7ea ("mm: device exclusive memory access") we can return with a device-exclusive entry from page_vma_mapped_walk(). page_vma_mkclean_one() is not prepared for that, so teach it about these PFN swap PTEs. Note that device-private entries are so far not applicable on that path, as we expect ZONE_DEVICE pages so far only in migration code when it comes to the RMAP. Note that we could currently only run into this case with device-exclusive entries on THPs. We still adjust the mapcount on conversion to device-exclusive; this makes the rmap walk abort early for small folios, because we'll always have !folio_mapped() with a single device-exclusive entry. We'll adjust the mapcount logic once all page_vma_mapped_walk() users can properly handle device-exclusive entries. Fixes: b756a3b5e7ea ("mm: device exclusive memory access") Signed-off-by: David Hildenbrand --- mm/rmap.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/rmap.c b/mm/rmap.c index 7c471c3ea64c4..7b737f0f68fb5 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1044,6 +1044,14 @@ static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw) pte_t *pte = pvmw->pte; pte_t entry = ptep_get(pte); + /* + * PFN swap PTEs, such as device-exclusive ones, that + * actually map pages are clean and not writable from a + * CPU perspective. The MMU notifier takes care of any + * device aspects. + */ + if (!pte_present(entry)) + continue; if (!pte_dirty(entry) && !pte_write(entry)) continue; -- 2.48.1