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Thu, 5 Nov 2026 17:00:56 +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 HMEkC0K27GqWRwAAD6G6ig:T5 (envelope-from ); Thu, 05 Nov 2026 17:00:56 +0000 From: =?UTF-8?q?Carlos=20L=C3=B3pez?= To: kvm@vger.kernel.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-riscv@lists.infradead.org, seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org, david@kernel.org, peterx@redhat.com, ljs@kernel.org, imbrenda@linux.ibm.com, borntraeger@linux.ibm.com, frankja@linux.ibm.com, =?UTF-8?q?Carlos=20L=C3=B3pez?= , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato Subject: [PATCH v2 4/9] mm/mprotect: add MM_CP_PERM_UPGRADE Date: Thu, 5 Nov 2026 17:50:01 +0100 Message-ID: <20261105165004.2663799-8-clopez@suse.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20261105165004.2663799-4-clopez@suse.de> References: <20261105165004.2663799-4-clopez@suse.de> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-12.30 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[22]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -12.30 X-Spam-Level: X-Spam-Flag: NO Add a change_protection() flag for changes that only add permissions, keeping the PFN and revoking no access. mprotect() sets it when the new VMA flags only add read, write or execute permissions. VM_ACCOUNT may be added as well, as it does not affect the page tables. Any other change, such as a different protection key, is not considered an upgrade. This will allow MMU notifier users to perform optimizations, as they can avoid invalidating PTEs whose permissions can be faulted in. Signed-off-by: Carlos López --- include/linux/mm.h | 2 ++ mm/mprotect.c | 13 +++++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 9f167950926a..dddbd76a2760 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3581,6 +3581,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); #define MM_CP_UFFD_RWP_RESOLVE (1UL << 5) /* resolve rwp */ #define MM_CP_UFFD_RWP_ALL (MM_CP_UFFD_RWP | \ MM_CP_UFFD_RWP_RESOLVE) +/* Whether this change only upgrades/adds permissions */ +#define MM_CP_PERM_UPGRADE (1UL << 6) bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, pte_t pte); diff --git a/mm/mprotect.c b/mm/mprotect.c index 754333698c1e..683131c9c4a0 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -756,6 +756,17 @@ static const struct mm_walk_ops prot_none_walk_ops = { .walk_lock = PGWALK_WRLOCK, }; +static bool vma_flags_is_perm_upgrade(vma_flags_t old_vma_flags, + vma_flags_t new_vma_flags) +{ + vm_flags_t old = vma_flags_to_legacy(old_vma_flags); + vm_flags_t new = vma_flags_to_legacy(new_vma_flags); + /* VM_ACCOUNT does not affect page tables */ + vm_flags_t mask = VM_READ | VM_WRITE | VM_EXEC | VM_ACCOUNT; + + return new == (old | (new & mask)); +} + int mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, struct vm_area_struct *vma, struct vm_area_struct **pprev, @@ -836,6 +847,8 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, vma_flags_reset_once(vma, &new_vma_flags); if (vma_wants_manual_pte_write_upgrade(vma)) mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; + if (vma_flags_is_perm_upgrade(old_vma_flags, new_vma_flags)) + mm_cp_flags |= MM_CP_PERM_UPGRADE; vma_set_page_prot(vma); change_protection(tlb, vma, start, end, mm_cp_flags); -- 2.51.0