From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=195.135.223.131 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794493541; b=0rmNC8sog6ii/45JmDOjheJnGEIJgOqc8kMKtZnh2AQpzIJ+qqXLlOLpYx5hQGpiGbWJ C+PZfjSqg8yJ6goscwh6lwgdI6izHcnZjzOWeVmBY2UyVuXETztpGj8UhMaTalvfF8dfU hkz+I9r+jh08hWEvElcEqKh1sHL2ypK7kDyWzy5RUyegkkaEore0AGJhLUrvmYFLhZwUt eSIZoAOL67SjEdf/OwCMWHklcVClBN7Ph6DxPKnLwjbofGm7NquvV1A5aJiLKXf3N5ODq Rbh12QWbNDJCYEZS9a/KEJpKPjul5a1ZamJu/0ZxU2gbB7XY7T7E0B7DdWho7TI18Zg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794493541; h=DMARC-Filter:Received:Received:Received:From:To:Cc:Subject:Date: Message-ID:X-Mailer:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding:X-Rspamd-Pre-Result:X-Rspamd-Queue-Id: X-Rspamd-Pre-Result:X-Rspamd-Action:X-Rspamd-Server:X-Spam-Level: X-Spamd-Result:X-Spam-Flag:X-Spam-Score; bh=AcG4jQDK10PWiWbm7mNfeb+DWsCeA1RxCscXblM2xnQ=; b=KQZ5rHBrthlkkJcnZhBly9zLmX+/nvZA8+51W9XKI5FD1dPt7sjiPeS8In64lu9DpbFv DCoa3s3P2BMM5FVFFC43HJXG6SKNlxf+8fmV0NC1z9rNYFx+Bjrsz75+6zL2mugaR8YEC ElE6dgWB/i7kAABQ6lcWb9iW2zi4zhVNHuym/Mjy6k6oOidTsBxNOyVaUAjjMOZ3E3lch u+Q9zyq7oBzHEQpFkV1+6KoiRwcpnWskqtqxew4ytT0uZSJpiVbB66OaBJneQ8OUNe/WL sEBD9DiyDdmNvWXpu8QCgc4DQwgeczXtHPxnZMoVgdqGOyIjI50xCFZBN472qXrTwGg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=suse.de; spf=pass smtp.mailfrom=suse.de; arc=none smtp.remote-ip=195.135.223.131 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5D5E8606B094; Thu, 12 Nov 2026 14:25:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5D5E8606B094 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id B0A701F7A3; Thu, 12 Nov 2026 14:25:39 +0000 (UTC) Authentication-Results: smtp-out2.suse.de; none Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 5BE6013432; Thu, 12 Nov 2026 14:25:38 +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 w9GzDFnM9WoAPwAAD6G6ig:T7 (envelope-from ); Thu, 12 Nov 2026 14:25:38 +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 , Muchun Song , Oscar Salvador , Jann Horn , Pedro Falcato Subject: [PATCH v3 6/9] mm/mmu_notifier: add MMU_NOTIFIER_RANGE_PERM_UPGRADE Date: Thu, 12 Nov 2026 15:20:35 +0100 Message-ID: <20261112142039.907090-8-clopez@suse.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20261112142039.907090-2-clopez@suse.de> References: <20261112142039.907090-2-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-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Queue-Id: B0A701F7A3 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Level: X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[] X-Spam-Flag: NO X-Spam-Score: -4.00 Add a range flag for invalidations that only upgrade permissions, so that secondary MMUs can keep their mappings rather than zap them. change_protection() sets it for MM_CP_PERM_UPGRADE and for the userfaultfd resolves, which only restore access. Now that change_protection() keeps writable entries writable on these changes, no present entry loses access. Writable migration and device-private entries are still made read-only, which does not affect secondary MMUs. Migration entries are only installed after secondary MMUs are invalidated, and device-private pages are migrated back, with an invalidation, before the CPU can access them. hugetlb_change_protection() never sets the flag, as hugetlb does not restore the write bit and may unshare page tables. Signed-off-by: Carlos López --- include/linux/mmu_notifier.h | 5 +++++ mm/hugetlb.c | 4 ++++ mm/internal.h | 7 +++++++ mm/mprotect.c | 5 +++-- 4 files changed, 19 insertions(+), 2 deletions(-) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index 5db78e5761c5..b2f186ebacf9 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 ce9c8e57b8e5..06fd31b8fbc4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6632,6 +6632,10 @@ long hugetlb_change_protection(struct vm_area_struct *vma, * 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_PERM_UPGRADE is never set here. hugetlb does not + * restore the write bit, and huge_pmd_unshare() may drop the mapping, + * so this is not a strict permission upgrade. */ mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, mm, start, end); diff --git a/mm/internal.h b/mm/internal.h index e3f92883bf23..b74ea18c6103 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1453,6 +1453,13 @@ static inline bool pte_needs_soft_dirty_wp(struct vm_area_struct *vma, pte_t pte return vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte); } +/* Whether a change_protection() only adds permissions. */ +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); +} + /* shrinker related functions */ unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg, int priority); diff --git a/mm/mprotect.c b/mm/mprotect.c index 8c0fcd10f5a3..b7accf60c3d4 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -608,8 +608,9 @@ static inline long change_pud_range(struct mmu_gather *tlb, continue; if (!range.start) { - mmu_notifier_range_init(&range, - MMU_NOTIFY_PROTECTION_VMA, 0, + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, + mm_cp_is_perm_upgrade(cp_flags) ? + MMU_NOTIFIER_RANGE_PERM_UPGRADE : 0, vma->vm_mm, addr, end); mmu_notifier_invalidate_range_start(&range); } -- 2.51.0