From nobody Mon Feb 9 19:30:12 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=arm.com ARC-Seal: i=1; a=rsa-sha256; t=1621255115; cv=none; d=zohomail.com; s=zohoarc; b=fY7vKOJsESma0BR+BN7KfNv5IgCsUpPfz1vHnbiHhRoxID0Ra0z1CnkwOGZ+HprLiPy5f62scdrPK2u3eKOLivsg+WBazf3nyNFaFS8X6Um36tdkkxRwwXW3BImLCTL7WxjB8Q8j1/Pg5wYynw/+ym99ftuBtUcjIcjNI+BFT/0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1621255115; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=0W1nZf8P62jq7aJJTg+zey+rtb45cVk0Y2HYC+sNqGs=; b=kdmMc0vAYthjAP2Ctl7LaOKoiyJAAkCJlBhyE6jxS9o8Rfrf7xGFfeJEjab7QfX7f9KhuB8ZZUgbjfu8HZnRCW3Vic0/DIetW8ewcV26Yow4Biu8u6XNqdclXdF6FMAXDGCb4w1XjCQk/ky1bCPuJ1mcvHEhtFH3WwZiGQvtchs= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1621255115864644.4733261007; Mon, 17 May 2021 05:38:35 -0700 (PDT) Received: from localhost ([::1]:53754 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1licW2-00022A-OG for importer@patchew.org; Mon, 17 May 2021 08:38:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54072) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1licR0-0006qa-2P for qemu-devel@nongnu.org; Mon, 17 May 2021 08:33:22 -0400 Received: from foss.arm.com ([217.140.110.172]:42762) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1licQy-0007qm-2z for qemu-devel@nongnu.org; Mon, 17 May 2021 08:33:21 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 346A1113E; Mon, 17 May 2021 05:33:19 -0700 (PDT) Received: from e112269-lin.arm.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2CBBB3F73B; Mon, 17 May 2021 05:33:16 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Subject: [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Date: Mon, 17 May 2021 13:32:34 +0100 Message-Id: <20210517123239.8025-4-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210517123239.8025-1-steven.price@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=217.140.110.172; envelope-from=steven.price@arm.com; helo=foss.arm.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Peter Maydell , "Dr. David Alan Gilbert" , Andrew Jones , Haibo Xu , Suzuki K Poulose , qemu-devel@nongnu.org, Dave Martin , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Steven Price , James Morse , Julien Thierry , Thomas Gleixner , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" A KVM guest could store tags in a page even if the VMM hasn't mapped the page with PROT_MTE. So when restoring pages from swap we will need to check to see if there are any saved tags even if !pte_tagged(). However don't check pages for which pte_access_permitted() returns false as these will not have been swapped out. Signed-off-by: Steven Price --- arch/arm64/include/asm/pgtable.h | 9 +++++++-- arch/arm64/kernel/mte.c | 16 ++++++++++++++-- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index 0b10204e72fc..275178a810c1 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -314,8 +314,13 @@ static inline void set_pte_at(struct mm_struct *mm, un= signed long addr, if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte)) __sync_icache_dcache(pte); =20 - if (system_supports_mte() && - pte_present(pte) && pte_tagged(pte) && !pte_special(pte)) + /* + * If the PTE would provide user space access to the tags associated + * with it then ensure that the MTE tags are synchronised. Exec-only + * mappings don't expose tags (instruction fetches don't check tags). + */ + if (system_supports_mte() && pte_present(pte) && + pte_access_permitted(pte, false) && !pte_special(pte)) mte_sync_tags(ptep, pte); =20 __check_racy_pte_update(mm, ptep, pte); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index c88e778c2fa9..a604818c52c1 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -33,11 +33,15 @@ DEFINE_STATIC_KEY_FALSE(mte_async_mode); EXPORT_SYMBOL_GPL(mte_async_mode); #endif =20 -static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_= swap) +static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_= swap, + bool pte_is_tagged) { unsigned long flags; pte_t old_pte =3D READ_ONCE(*ptep); =20 + if (!is_swap_pte(old_pte) && !pte_is_tagged) + return; + spin_lock_irqsave(&tag_sync_lock, flags); =20 /* Recheck with the lock held */ @@ -53,6 +57,9 @@ static void mte_sync_page_tags(struct page *page, pte_t *= ptep, bool check_swap) } } =20 + if (!pte_is_tagged) + goto out; + page_kasan_tag_reset(page); /* * We need smp_wmb() in between setting the flags and clearing the @@ -76,10 +83,15 @@ void mte_sync_tags(pte_t *ptep, pte_t pte) bool check_swap =3D nr_pages =3D=3D 1; bool pte_is_tagged =3D pte_tagged(pte); =20 + /* Early out if there's nothing to do */ + if (!check_swap && !pte_is_tagged) + return; + /* if PG_mte_tagged is set, tags have already been initialised */ for (i =3D 0; i < nr_pages; i++, page++) { if (!test_bit(PG_mte_tagged, &page->flags)) - mte_sync_page_tags(page, ptep, check_swap); + mte_sync_page_tags(page, ptep, check_swap, + pte_is_tagged); } } =20 --=20 2.20.1