From nobody Mon Feb 9 20:59:57 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=1621853334; cv=none; d=zohomail.com; s=zohoarc; b=cIXOWZj/f16Q5Y0fzg2p/Ic9c0Ac8yotiSL9EKWk8bHHBwZi7OGgOmffn9SyifDTqy+hBkV0nlDCI+gCz6x07l1SaqYxvaTij5XxFl9KyPiXPQjk/AuyCYwMneoLTGKcLas8APtDB6jeYfGzoKDVOmVDwwB8HZST0V02ckydvTw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1621853334; 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=wnZXS9XwrqSpnL+PRnOEfeynBYu3v9txEd7Q12QOYso=; b=WuP7TZbEZxvIWqVzUTNVi95C5/iUhmucrB5MD0oP+6rA51xiRr/u/vMzTj31kXZHKKAh+jPGYi/sKyDhPi7FQpHwbrz5zG4tEp2XSEhaxHgXTzjbqzGh+581IJUDn4nAg78LgoCi2+PshJKYlJ6ULxisfJrGtYqlEErzKVH8LgM= 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 1621853334194638.747346138194; Mon, 24 May 2021 03:48:54 -0700 (PDT) Received: from localhost ([::1]:51796 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ll88j-0004Cc-6W for importer@patchew.org; Mon, 24 May 2021 06:48:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48442) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ll85W-0005Ej-IV for qemu-devel@nongnu.org; Mon, 24 May 2021 06:45:34 -0400 Received: from foss.arm.com ([217.140.110.172]:33462) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ll85U-0005Fq-9d for qemu-devel@nongnu.org; Mon, 24 May 2021 06:45:34 -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 58E51139F; Mon, 24 May 2021 03:45:31 -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 941653F719; Mon, 24 May 2021 03:45:28 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Subject: [PATCH v13 3/8] arm64: mte: Sync tags for pages where PTE is untagged Date: Mon, 24 May 2021 11:45:08 +0100 Message-Id: <20210524104513.13258-4-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210524104513.13258-1-steven.price@arm.com> References: <20210524104513.13258-1-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 Reviewed-by: Catalin Marinas --- arch/arm64/include/asm/mte.h | 4 ++-- arch/arm64/include/asm/pgtable.h | 22 +++++++++++++++++++--- arch/arm64/kernel/mte.c | 16 ++++++++++++---- 3 files changed, 33 insertions(+), 9 deletions(-) diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index bc88a1ced0d7..347ef38a35f7 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -37,7 +37,7 @@ void mte_free_tag_storage(char *storage); /* track which pages have valid allocation tags */ #define PG_mte_tagged PG_arch_2 =20 -void mte_sync_tags(pte_t *ptep, pte_t pte); +void mte_sync_tags(pte_t old_pte, pte_t pte); void mte_copy_page_tags(void *kto, const void *kfrom); void mte_thread_init_user(void); void mte_thread_switch(struct task_struct *next); @@ -53,7 +53,7 @@ int mte_ptrace_copy_tags(struct task_struct *child, long = request, /* unused if !CONFIG_ARM64_MTE, silence the compiler */ #define PG_mte_tagged 0 =20 -static inline void mte_sync_tags(pte_t *ptep, pte_t pte) +static inline void mte_sync_tags(pte_t old_pte, pte_t pte) { } static inline void mte_copy_page_tags(void *kto, const void *kfrom) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index 0b10204e72fc..db5402168841 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -314,9 +314,25 @@ 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)) - mte_sync_tags(ptep, pte); + /* + * If the PTE would provide user space access to the tags associated + * with it then ensure that the MTE tags are synchronised. Although + * pte_access_permitted() returns false for exec only mappings, they + * don't expose tags (instruction fetches don't check tags). + */ + if (system_supports_mte() && pte_access_permitted(pte, false) && + !pte_special(pte)) { + pte_t old_pte =3D READ_ONCE(*ptep); + /* + * We only need to synchronise if the new PTE has tags enabled + * or if swapping in (in which case another mapping may have + * set tags in the past even if this PTE isn't tagged). + * (!pte_none() && !pte_present()) is an open coded version of + * is_swap_pte() + */ + if (pte_tagged(pte) || (!pte_none(old_pte) && !pte_present(old_pte))) + mte_sync_tags(old_pte, pte); + } =20 __check_racy_pte_update(mm, ptep, pte); =20 diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 45fac0e9c323..ae0a3c68fece 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -33,10 +33,10 @@ 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 old_pte, + bool check_swap, bool pte_is_tagged) { unsigned long flags; - pte_t old_pte =3D READ_ONCE(*ptep); =20 spin_lock_irqsave(&tag_sync_lock, flags); =20 @@ -53,6 +53,9 @@ 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 @@ -69,17 +72,22 @@ static void mte_sync_page_tags(struct page *page, pte_t= *ptep, bool check_swap) spin_unlock_irqrestore(&tag_sync_lock, flags); } =20 -void mte_sync_tags(pte_t *ptep, pte_t pte) +void mte_sync_tags(pte_t old_pte, pte_t pte) { struct page *page =3D pte_page(pte); long i, nr_pages =3D compound_nr(page); 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, old_pte, check_swap, + pte_is_tagged); } } =20 --=20 2.20.1