From nobody Sun Dec 14 11:48:40 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18A6513DBBC for ; Wed, 14 Feb 2024 20:44:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707943496; cv=none; b=Y3V+yIn06K/QstJVfZqzPnt/iOFoqtnJluMeJolj39Bp39NOq81Lzan6Qo0hSfTEqZIBQ+hy/PzcsfxTWOxuLJRJKtRJ8+ZVp2VRqFC5df2W3XCvgkbWwmaGXyh/Zo64rU6eVpwtsABytcD96FdEc9D4QbmgGgVY8Gl9K9TLDB4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707943496; c=relaxed/simple; bh=iKdLPd0l+BlZy4NkWR4PBv4pdjA5DJYrKJe9pxJlmq0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dCoi4CZ7czrQ0+oxLVAMmUE3EXlMZkyWYMgt8/YiZd42WXBTZdFZx4z+DnSiQMVrsz+GW8BBNN6dca1DwUm4IZvzH+TKqqcU6y8YunovGeJ5TF8gjfeIumeLLdNopxlhuGRTf3LfohDXJ6wMy50fLe7zF0iToeNYPR2/p0jnKm8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=W1RBDJtB; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="W1RBDJtB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707943493; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fqQsnr9EFuS72Lg9egurC5IFPM5MYMM8dNEJpcWm/gk=; b=W1RBDJtBwg9W+BfbT6HUgiiUvjjcIhM0oPUPegvDgLyLaH1uQ/3AzflJdVNzp2tC4YUDsy uRhtK9g5gZ9McblshTAH4b4FlMMINq8sVeqO9aDns+7hQrQuI7QQL/fzhA8jaluOp7a7zs x97Xozf/J+DBpyapPn2gKITmhtTbtJY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-226-pgh-LenmOMa4VgIEuXmFnA-1; Wed, 14 Feb 2024 15:44:50 -0500 X-MC-Unique: pgh-LenmOMa4VgIEuXmFnA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0A351185A782; Wed, 14 Feb 2024 20:44:49 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.39.194.174]) by smtp.corp.redhat.com (Postfix) with ESMTP id 438201C066AA; Wed, 14 Feb 2024 20:44:45 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Matthew Wilcox , Ryan Roberts , Catalin Marinas , Yin Fengwei , Michal Hocko , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Michael Ellerman , Christophe Leroy , "Naveen N. Rao" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org Subject: [PATCH v3 02/10] mm/memory: handle !page case in zap_present_pte() separately Date: Wed, 14 Feb 2024 21:44:27 +0100 Message-ID: <20240214204435.167852-3-david@redhat.com> In-Reply-To: <20240214204435.167852-1-david@redhat.com> References: <20240214204435.167852-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Content-Type: text/plain; charset="utf-8" We don't need uptodate accessed/dirty bits, so in theory we could replace ptep_get_and_clear_full() by an optimized ptep_clear_full() function. Let's rely on the provided pte. Further, there is no scenario where we would have to insert uffd-wp markers when zapping something that is not a normal page (i.e., zeropage). Add a sanity check to make sure this remains true. should_zap_folio() no longer has to handle NULL pointers. This change replaces 2/3 "!page/!folio" checks by a single "!page" one. Note that arch_check_zapped_pte() on x86-64 checks the HW-dirty bit to detect shadow stack entries. But for shadow stack entries, the HW dirty bit (in combination with non-writable PTEs) is set by software. So for the arch_check_zapped_pte() check, we don't have to sync against HW setting the HW dirty bit concurrently, it is always set. Reviewed-by: Ryan Roberts Signed-off-by: David Hildenbrand --- mm/memory.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 5b0dc33133a6..4da6923709b2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1497,10 +1497,6 @@ static inline bool should_zap_folio(struct zap_detai= ls *details, if (should_zap_cows(details)) return true; =20 - /* E.g. the caller passes NULL for the case of a zero folio */ - if (!folio) - return true; - /* Otherwise we should only zap non-anon folios */ return !folio_test_anon(folio); } @@ -1538,24 +1534,28 @@ static inline void zap_present_pte(struct mmu_gathe= r *tlb, int *rss, bool *force_flush, bool *force_break) { struct mm_struct *mm =3D tlb->mm; - struct folio *folio =3D NULL; bool delay_rmap =3D false; + struct folio *folio; struct page *page; =20 page =3D vm_normal_page(vma, addr, ptent); - if (page) - folio =3D page_folio(page); + if (!page) { + /* We don't need up-to-date accessed/dirty bits. */ + ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); + arch_check_zapped_pte(vma, ptent); + tlb_remove_tlb_entry(tlb, pte, addr); + VM_WARN_ON_ONCE(userfaultfd_wp(vma)); + ksm_might_unmap_zero_page(mm, ptent); + return; + } =20 + folio =3D page_folio(page); if (unlikely(!should_zap_folio(details, folio))) return; ptent =3D ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); arch_check_zapped_pte(vma, ptent); tlb_remove_tlb_entry(tlb, pte, addr); zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); - if (unlikely(!page)) { - ksm_might_unmap_zero_page(mm, ptent); - return; - } =20 if (!folio_test_anon(folio)) { if (pte_dirty(ptent)) { --=20 2.43.0