From nobody Fri Oct 24 20:23:17 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A25FDC25B08 for ; Mon, 15 Aug 2022 21:48:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349898AbiHOVs5 (ORCPT ); Mon, 15 Aug 2022 17:48:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349746AbiHOVq0 (ORCPT ); Mon, 15 Aug 2022 17:46:26 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C76F9C9EBF; Mon, 15 Aug 2022 12:30:12 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6ABA5B810C6; Mon, 15 Aug 2022 19:30:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B736CC433D6; Mon, 15 Aug 2022 19:30:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660591810; bh=1aEBkEVldE0y9BjO7ITmcEY/CmdEXYwxIU4S5/DA+5M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zbI4BhQNmNNLKOO7VUqdFLfqdIGd2IvSAu+sNi8CpFlKOdjrgcFfJQv1LSD7DeNsG MPDKCs3KuPj5mYg7UI6X87lcs7CV9jUhHx2QGq5tWSpBTe7huVDU562DyffVCBefWp OBIW0F2tNU8HwDH9TC3vkCswavTlNsO1hnoXrQgA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Christopherson , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.18 0684/1095] KVM: Dont set Accessed/Dirty bits for ZERO_PAGE Date: Mon, 15 Aug 2022 20:01:23 +0200 Message-Id: <20220815180457.671221396@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180429.240518113@linuxfoundation.org> References: <20220815180429.240518113@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Sean Christopherson [ Upstream commit a1040b0d42acf69bb4f6dbdc54c2dcd78eea1de5 ] Don't set Accessed/Dirty bits for a struct page with PG_reserved set, i.e. don't set A/D bits for the ZERO_PAGE. The ZERO_PAGE (or pages depending on the architecture) should obviously never be written, and similarly there's no point in marking it accessed as the page will never be swapped out or reclaimed. The comment in page-flags.h is quite clear that PG_reserved pages should be managed only by their owner, and strictly following that mandate also simplifies KVM's logic. Fixes: 7df003c85218 ("KVM: fix overflow of zero page refcount with ksm runn= ing") Signed-off-by: Sean Christopherson Message-Id: <20220429010416.2788472-4-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/kvm_main.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6c8295e76548..843396ed4ad3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2852,16 +2852,28 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn) } EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty); =20 +static bool kvm_is_ad_tracked_pfn(kvm_pfn_t pfn) +{ + if (!pfn_valid(pfn)) + return false; + + /* + * Per page-flags.h, pages tagged PG_reserved "should in general not be + * touched (e.g. set dirty) except by its owner". + */ + return !PageReserved(pfn_to_page(pfn)); +} + void kvm_set_pfn_dirty(kvm_pfn_t pfn) { - if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn)) + if (kvm_is_ad_tracked_pfn(pfn)) SetPageDirty(pfn_to_page(pfn)); } EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty); =20 void kvm_set_pfn_accessed(kvm_pfn_t pfn) { - if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn)) + if (kvm_is_ad_tracked_pfn(pfn)) mark_page_accessed(pfn_to_page(pfn)); } EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed); --=20 2.35.1