From mboxrd@z Thu Jan 1 00:00:00 1970 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 31876C00140 for ; Mon, 15 Aug 2022 19:10:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343715AbiHOTKf (ORCPT ); Mon, 15 Aug 2022 15:10:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245416AbiHOTHT (ORCPT ); Mon, 15 Aug 2022 15:07:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 360AEB4A8; Mon, 15 Aug 2022 11:35:27 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 538A761019; Mon, 15 Aug 2022 18:35:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E4A5C433C1; Mon, 15 Aug 2022 18:35:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660588525; bh=cBQfniI4oyotMAIDfEeA5mZb0s7lj68v4X9HLUHZcQ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2tPkL/CTUpyfxiWPLUXPy0pHBI0m2pmLpUsKFcp18A6BzA+KRQ6/91ASDc54xJant mXQuAkKnfJokEREM2GroBGcp5KSaFISAp0MLYpiSq1pT3sIrRaa59Ccxg5eHb/HF4X OxxOLkrCZiXb1RB+E2DDdocdwWyoMJ7lFKFBNgps= 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 5.15 432/779] KVM: Dont set Accessed/Dirty bits for ZERO_PAGE Date: Mon, 15 Aug 2022 20:01:16 +0200 Message-Id: <20220815180355.752261884@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180337.130757997@linuxfoundation.org> References: <20220815180337.130757997@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 running") 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 0816b8018cde..251b4143f505 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2762,16 +2762,28 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn) } EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty); +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); 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); -- 2.35.1