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=1793898055; b=w7+FpIwFBy+QnjpfB/Mlgo13lIrFWtPNJC+o5JhWx5oOkITKcQtwtTLkyF4Qt2X3l1wY Djvz9H2jtrClK68zFb/xQeLkOoxlTyYCR2uDPgryk9ubeZGPhvYqxxHo6n4lTR9q3jAs8 Plm5yrcrnJ5VqG4qm6ZKT7Z0KRQ1a7GXCQVSHtm1if+RUZpFFtE2bMNQti9lfrMPP1fWH aCjYZIeML7I7cMepMTuPOqHEUcGrgQxjoYjvyXebYuMCNQ3V7Vrp8h4yswxmAgYnaLDK9 knzNS16oBtn6a+7Cr04dVMh6wO/hTSf/6qNMnaI/OGHniWlYLw87xNjmAPJnbtVEceg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793898055; h=DMARC-Filter:Received:DKIM-Signature:DKIM-Signature:DKIM-Signature: DKIM-Signature:Received:Received:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding:X-Spamd-Result:X-Rspamd-Server: X-Rspamd-Action:X-Spam-Flag:X-Spam-Score:X-Spam-Level: X-Rspamd-Queue-Id; bh=wLnVsJjCToHG/C28VTmqNBcIFpk1g6vauHuX2+bvyeo=; b=FeOqzX1mC11Turd3irXuv1J2cyK0KNHRetp5TQP4efE+KP/d5saYOYpHquJSRirLa3V9 UUGW89ydGPH1xlK+kIgoyXHqiBXS/QO8/Q5eSvso+OwHNhZJ0KyX89T6QzQX8NNMRZTFg 6QGOhKKjJsCYVB41HaINYo7NeuK8cFackf8Ve9I7uZnQNtChChUME7ebkzWKysGVjgObM ZYupzVNmPn3BehqnoE7ZED4dUpuUmDE/yublB8SR/Y35KYRFGYxF16yCy6gnD1eM8KNMY 49qWSAxmkUOi7193L/lN0CPI4hK6sqRPIilHWcAxP0bov9z+UopKPFdFqYEW/sK0fNw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass header.d=suse.de header.i=@suse.de header.a=rsa-sha256 header.s=susede2_rsa header.b="AtWih/Q5"; dkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256 header.s=susede2_ed25519 header.b="/1ksPkT9"; dkim=pass header.d=suse.de header.i=@suse.de header.a=rsa-sha256 header.s=susede2_rsa header.b="AtWih/Q5"; dkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256 header.s=susede2_ed25519 header.b="/1ksPkT9"; 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 E290B606A31B; Thu, 5 Nov 2026 17:00:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org E290B606A31B 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=suse.de header.i=@suse.de header.a=rsa-sha256 header.s=susede2_rsa header.b=AtWih/Q5; dkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256 header.s=susede2_ed25519 header.b=/1ksPkT9; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.a=rsa-sha256 header.s=susede2_rsa header.b=AtWih/Q5; dkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256 header.s=susede2_ed25519 header.b=/1ksPkT9 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 32F211FB3F; Thu, 5 Nov 2026 17:00:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1793898053; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wLnVsJjCToHG/C28VTmqNBcIFpk1g6vauHuX2+bvyeo=; b=AtWih/Q5UNeIcyR295m20gTBxLNQQlEW/6jV44r/WyqnpGBlFrxfzrmeI4eK5R/FG9mP8B 5UwO65a5cCQ1VzYek0nbWAcmTzFXkXz50rqaQTjIh5y0Ds3XEVC9sq3K8x0IZsLdslgQ+1 YvtRNvhR6Xxc9QjvOip6VNdLyvZvEFg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1793898053; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wLnVsJjCToHG/C28VTmqNBcIFpk1g6vauHuX2+bvyeo=; b=/1ksPkT9jyto6rEIVfPDgN8Dim3k3Ljbfr+TqqyZUZIMXx716QVdLySR0RyEa8lGTYD3/4 QsAvYC5IPlJGx8Aw== Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b="AtWih/Q5"; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b="/1ksPkT9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1793898053; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wLnVsJjCToHG/C28VTmqNBcIFpk1g6vauHuX2+bvyeo=; b=AtWih/Q5UNeIcyR295m20gTBxLNQQlEW/6jV44r/WyqnpGBlFrxfzrmeI4eK5R/FG9mP8B 5UwO65a5cCQ1VzYek0nbWAcmTzFXkXz50rqaQTjIh5y0Ds3XEVC9sq3K8x0IZsLdslgQ+1 YvtRNvhR6Xxc9QjvOip6VNdLyvZvEFg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1793898053; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wLnVsJjCToHG/C28VTmqNBcIFpk1g6vauHuX2+bvyeo=; b=/1ksPkT9jyto6rEIVfPDgN8Dim3k3Ljbfr+TqqyZUZIMXx716QVdLySR0RyEa8lGTYD3/4 QsAvYC5IPlJGx8Aw== 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 C24CE134F6; Thu, 5 Nov 2026 17:00:51 +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:T2 (envelope-from ); Thu, 05 Nov 2026 17:00:51 +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 , Jann Horn , Pedro Falcato , Peter Feiner Subject: [PATCH v2 1/9] mm: fix eager write-bit restore for write-notified shared mappings Date: Thu, 5 Nov 2026 17:49:58 +0100 Message-ID: <20261105165004.2663799-5-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 [-12.51 / 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]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[20]; RCVD_TLS_ALL(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -12.51 X-Spam-Level: X-Rspamd-Queue-Id: 32F211FB3F change_protection() applies vma->vm_page_prot, which lacks the write bit for CoW and write-notified mappings. To avoid needless write faults, callers set MM_CP_TRY_CHANGE_WRITABLE when vma_wants_manual_pte_write_upgrade() returns true, so that entries that can be written without a fault, such as dirty PTEs in a shared mapping, are made writable right away. For shared mappings, that function passes vma->vm_page_prot to vma_wants_writenotify(). Once writenotify is enabled, this protection lacks the write bit, while the vma_pgprot_modify() result it is compared against adds it back. The two never match, so vma_wants_writenotify() returns false before checking for soft-dirty, uffd-wp and writeback. As a result, write-notified shmem mappings never get MM_CP_TRY_CHANGE_WRITABLE, and their dirty PTEs stay read-only after a protection change. For example, commit 931298e103c2 ("mm/userfaultfd: rely on vma->vm_page_prot in uffd_wp_range()") made uffd-wp unprotect set MM_CP_TRY_CHANGE_WRITABLE so that dirty shmem PTEs become writable again, but this never takes effect. Unprotecting N dirty shmem pages still leads to N faults that only set the write bit. This dates back to the commit in the Fixes tag, which moved the equivalent check in mprotect_fixup() before vma_set_page_prot(). Fix this by passing the protection recomputed from the VMA flags, as vma_set_page_prot() does. Note that this is a performance-only fix, as the write bit is restored on the next page fault anyway. Fixes: 64e455079e1b ("mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared") Signed-off-by: Carlos López --- mm/vma.h | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/mm/vma.h b/mm/vma.h index 3fc3b47a954b..e83700e248e4 100644 --- a/mm/vma.h +++ b/mm/vma.h @@ -589,6 +589,14 @@ int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, unsigned long addr, int new_below); #endif +#ifdef CONFIG_MMU +static inline pgprot_t vma_pgprot_modify(pgprot_t oldprot, vma_flags_t vma_flags) +{ + const pgprot_t prot = vma_flags_to_page_prot(vma_flags); + + return pgprot_modify(oldprot, prot); +} + static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma) { /* @@ -596,19 +604,16 @@ static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma * if we can't do that automatically for all PTEs in a mapping. For * private mappings, that's always the case when we have write * permissions as we properly have to handle COW. + * + * vma->vm_page_prot lacks the write bit if writenotify is already + * enabled, so pass it with the bits restored, as vma_set_page_prot() + * does. */ if (vma->vm_flags & VM_SHARED) - return vma_wants_writenotify(vma, vma->vm_page_prot); + return vma_wants_writenotify(vma, + vma_pgprot_modify(vma->vm_page_prot, vma->flags)); return !!(vma->vm_flags & VM_WRITE); } - -#ifdef CONFIG_MMU -static inline pgprot_t vma_pgprot_modify(pgprot_t oldprot, vma_flags_t vma_flags) -{ - const pgprot_t prot = vma_flags_to_page_prot(vma_flags); - - return pgprot_modify(oldprot, prot); -} #endif static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi, -- 2.51.0