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Thu, 29 Oct 2026 14:44:42 +0000 From: =?UTF-8?q?Carlos=20L=C3=B3pez?= To: kvm@vger.kernel.org, linux-mm@kvack.org, seanjc@google.com, pbonzini@redhat.com Cc: linux-s390@vger.kernel.org, imbrenda@linux.ibm.com, =?UTF-8?q?Carlos=20L=C3=B3pez?= , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Muchun Song , Oscar Salvador , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org (open list) Subject: [RFC PATCH 2/4] mm/mmu_notifier: add MMU_NOTIFIER_RANGE_PERM_UPGRADE Date: Thu, 29 Oct 2026 15:33:35 +0100 Message-ID: <20261029143336.390231-5-clopez@suse.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20261029143336.390231-3-clopez@suse.de> References: <20261029143336.390231-3-clopez@suse.de> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -16.30 X-Spam-Level: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E648D40011 X-Stat-Signature: p6fnubanz8rs47y91mgbxf167ie7yib4 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793285084-445210 X-HE-Meta: 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 dX8plpDK CHy+sTiOrWRJX99N4ryCkHuJ4gwdzNJN6OsuqxLZNeP6hD29DHCgaGdK7UiSENHcQMksUihn86zYXQzEEGpwrnzLTcvoxmCQmPF8WXxZ1MhNeA8VhptayiFcOyPDFDlcIUncGRBhY/VErqzkMErrZLN3u8RGPOJaw4B/Q3nwBM4qRSGKpbyfpTzTLCqRJUfmFNqPgpLakh4kSLEM22HzCt6hWSU3pu9Lhb9/Mrs6kDxjTo/rz7E40OnFdDzrnbc5W7VmXGsDWaGaX1rr5VK3uRrTF/GUZjUx3x6jcgDtLvX2yaCzJKnOJzqMOXjAs/EpShakOWrXb6uOLSaTMFoKHA7/tKIodPJ3M32nGYzBN9P3vLZs3rYbRuC0aYQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Add a range flag marking an invalidation that only upgrades permissions (that is, no PFN change and no revoked access). change_protection() sets it for MM_CP_PERM_UPGRADE and for the userfaultfd permission resolves, which unprotect a page and thus only restore access. A secondary MMU can use the flag to keep its mappings rather than zap them. Consumers that ignore it are unaffected. Signed-off-by: Carlos López --- include/linux/mm.h | 6 ++++++ include/linux/mmu_notifier.h | 5 +++++ mm/hugetlb.c | 6 +++++- mm/mprotect.c | 7 ++++++- 4 files changed, 22 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f406ce9d1032..c4fc3876a4b7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3418,6 +3418,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); /* Whether this change only upgrades/adds permissions */ #define MM_CP_PERM_UPGRADE (1UL << 6) +static inline bool mm_cp_is_perm_upgrade(unsigned long cp_flags) +{ + return cp_flags & (MM_CP_PERM_UPGRADE | MM_CP_UFFD_WP_RESOLVE | + MM_CP_UFFD_RWP_RESOLVE); +} + bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, pte_t pte); extern long change_protection(struct mmu_gather *tlb, diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index a11a44eef521..112be28cdf6b 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -60,6 +60,11 @@ enum mmu_notifier_event { }; #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0) +/* + * Set on an invalidation that only expands permissions without + * revoking any existing access, nor freeing/moving the underlying page. + */ +#define MMU_NOTIFIER_RANGE_PERM_UPGRADE (1 << 1) struct mmu_notifier_ops { /* diff --git a/mm/hugetlb.c b/mm/hugetlb.c index b017ae1dfd6f..68d44044fdd2 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6548,19 +6548,23 @@ long hugetlb_change_protection(struct vm_area_struct *vma, long pages = 0, psize = huge_page_size(h); struct mmu_notifier_range range; unsigned long last_addr_mask; + unsigned int mn_flags = 0; bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; bool uffd_rwp = cp_flags & MM_CP_UFFD_RWP; bool uffd_rwp_resolve = cp_flags & MM_CP_UFFD_RWP_RESOLVE; struct mmu_gather tlb; + if (mm_cp_is_perm_upgrade(cp_flags)) + mn_flags |= MMU_NOTIFIER_RANGE_PERM_UPGRADE; + /* * In the case of shared PMDs, the area to flush could be beyond * start/end. Set range.start/range.end to cover the maximum possible * range if PMD sharing is possible. */ mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, - 0, mm, start, end); + mn_flags, mm, start, end); adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); BUG_ON(address >= end); diff --git a/mm/mprotect.c b/mm/mprotect.c index e9b636809c42..b48d2fd3b7b5 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -597,8 +597,13 @@ static inline long change_pud_range(struct mmu_gather *tlb, continue; if (!range.start) { + unsigned int mn_flags = 0; + + if (mm_cp_is_perm_upgrade(cp_flags)) + mn_flags |= MMU_NOTIFIER_RANGE_PERM_UPGRADE; + mmu_notifier_range_init(&range, - MMU_NOTIFY_PROTECTION_VMA, 0, + MMU_NOTIFY_PROTECTION_VMA, mn_flags, vma->vm_mm, addr, end); mmu_notifier_invalidate_range_start(&range); } -- 2.51.0