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 X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADA12C48BE6 for ; Mon, 14 Jun 2021 09:05:51 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 598A3611CA for ; Mon, 14 Jun 2021 09:05:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 598A3611CA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 0D42A40667; Mon, 14 Jun 2021 05:05:51 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vAzsq6vjigMX; Mon, 14 Jun 2021 05:05:49 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CA40C49F82; Mon, 14 Jun 2021 05:05:49 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 3EEFD40762 for ; Mon, 14 Jun 2021 05:05:49 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id sEAqfkPy2czq for ; Mon, 14 Jun 2021 05:05:47 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7BE7649F5F for ; Mon, 14 Jun 2021 05:05:47 -0400 (EDT) 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 11D1911D4; Mon, 14 Jun 2021 02:05:47 -0700 (PDT) Received: from e112269-lin.arm.com (autoplooker.cambridge.arm.com [10.1.194.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 110F73F694; Mon, 14 Jun 2021 02:05:43 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Subject: [PATCH v15 2/7] arm64: mte: Sync tags for pages where PTE is untagged Date: Mon, 14 Jun 2021 10:05:20 +0100 Message-Id: <20210614090525.4338-3-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210614090525.4338-1-steven.price@arm.com> References: <20210614090525.4338-1-steven.price@arm.com> MIME-Version: 1.0 Cc: "Dr. David Alan Gilbert" , qemu-devel@nongnu.org, Dave Martin , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Steven Price , Thomas Gleixner , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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. Reviewed-by: Catalin Marinas Signed-off-by: Steven Price --- arch/arm64/include/asm/mte.h | 4 ++-- arch/arm64/include/asm/pgtable.h | 22 +++++++++++++++++++--- arch/arm64/kernel/mte.c | 17 +++++++++++++---- 3 files changed, 34 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 -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 -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/pgtable.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, unsigned long addr, if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte)) __sync_icache_dcache(pte); - 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 = 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); + } __check_racy_pte_update(mm, ptep, pte); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index a3583a7fd400..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 -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 = READ_ONCE(*ptep); spin_lock_irqsave(&tag_sync_lock, flags); @@ -53,6 +53,9 @@ static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) } } + if (!pte_is_tagged) + goto out; + page_kasan_tag_reset(page); /* * We need smp_wmb() in between setting the flags and clearing the @@ -69,16 +72,22 @@ static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) spin_unlock_irqrestore(&tag_sync_lock, flags); } -void mte_sync_tags(pte_t *ptep, pte_t pte) +void mte_sync_tags(pte_t old_pte, pte_t pte) { struct page *page = pte_page(pte); long i, nr_pages = compound_nr(page); bool check_swap = nr_pages == 1; + bool pte_is_tagged = pte_tagged(pte); + + /* 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 = 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); } } -- 2.20.1 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm