From patchwork Fri Nov 4 01:10:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Collingbourne X-Patchwork-Id: 13031160 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0FEA5C4332F for ; Fri, 4 Nov 2022 01:12:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:References: Mime-Version:Message-Id:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=mL8DrHKvR6APG5F1mVBtbdXlCnpIgOBYKu0aW0E7Ejc=; b=Ewd2PHF0W4/SDweQhvoIWOnl09 HavYzRmGvpb5fHrTZCFHxanApascGiWeIyEuqeMOncYjnKZpN9MNS5jK/h5+Ho7QJIIbBsFEoGiPd RehAhW4Bgu2cnWzEWir6OdheW2mQ5435ZPJDgU+BBh/CCa+pUsovLAyzvxJLEMEHdhbTd0wqIeiYw q8CzGs51wh+ul6ScP8jfYAuZ1RvA7YRfAK8w1hUCtB79nAAcguvwSPguYYvffyXZI0IEc4UJ3z5UY QJj1UCarDXHHjssLzCbe1rkmXMw+boRgeayxPZ4UG8YWOOdyx445eq2r6nYnjBBq5IXDCHK6MfcZ4 /fgnCizw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqlFN-0024jV-8M; Fri, 04 Nov 2022 01:11:49 +0000 Received: from mail-yb1-xb49.google.com ([2607:f8b0:4864:20::b49]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqlEn-0024ZB-Ov for linux-arm-kernel@lists.infradead.org; Fri, 04 Nov 2022 01:11:15 +0000 Received: by mail-yb1-xb49.google.com with SMTP id q62-20020a25d941000000b006cac1a4000cso3608111ybg.14 for ; Thu, 03 Nov 2022 18:11:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=6mnzUwFKSGYwAtpE1xFv9gtpg0y2n02h+GI3HAPbvY8=; b=pIj4J6rKpj852/Q01C4mc9rc/pcuFfYL2jyQcwAyRPaOhS500Pp7/p5yskHAxgL8cP 7LCNOvi+glFZ0370iDQQ3s/iLtL/P3E8VtKx/CoJcId2j9dIkOaRAqhXBZnPIi4RoU/+ RPIHekEUkM6NWbI93zX9qLqiDmT2tZ8+tT9RgNfkSEHdKAHT9tkjFfz1yg9CNHsOWjmr ZrKPkrXnYtaH6XtudOAlXUnrq+wECy2iOuqxabTODY4lGJPstOc8v85CLULfpZJQytAs Yur4rJ02r73brUx7I3oLBdegIfsdjkYWBVSmR5OenCbtDi9rPeD21F2pv4XU4f7yL1A7 uOAA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=6mnzUwFKSGYwAtpE1xFv9gtpg0y2n02h+GI3HAPbvY8=; b=mZ7KpkzSWawxxzlc8D4572sajaUFrTFPctmWhp62zcLyezkXoBw+2KOJLdWvws4Vbi zt67sZlmcSlIKWZSXJQLYt2f+N52fwSRJYxg7lEWeMlIb65n2b0VkVDfTuxms36/A3FI UiiwDCzHaCLxSLBP5PqFmcup+F/M5KeIQYVX+pWigMMKzCQWtb7+7yongO5fPznIoJyL 07wLVKBDyq5V8FTphKUfEkQ/6sJwX5Ew77bHEdeu+f6ceyG/D0JJKnTMlJlBmydd2OLI j95ScmsYkThRX0vEasqNIz81nfwTE0zekH+TUus+yFb7T30aHIFNb6z0Gr8XwYC20scT H3Zg== X-Gm-Message-State: ACrzQf3VdXtwhI3ufvJRR+iKiO8C+cgDNxnVFc7EEAqW8eT22Bj707HG OIqObZihPUFvVeZZhj3gujhf+Ds2QgLUzU6fP7h/OMxckHiWnlIPSGB1WmOYo0kDWIk3soeBzz3 WLr0jtZOPhx4yFTYna5cOEsH0k7zXgJIItTLOioOA1tWYjBUH/erAIJCCiQ6JRHukkHGghWgz X-Google-Smtp-Source: AMsMyM7w0QK+CZrjKcOdzwSHLjGGRRGXKvvp9x9WLlsanFxQhoAT5hLo2bX5EUKBxxAnysQzH2/odis= X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2ce:200:2844:b0ec:e556:30d8]) (user=pcc job=sendgmr) by 2002:a0d:d702:0:b0:368:4ee7:b8c5 with SMTP id z2-20020a0dd702000000b003684ee7b8c5mr206390ywd.101.1667524271182; Thu, 03 Nov 2022 18:11:11 -0700 (PDT) Date: Thu, 3 Nov 2022 18:10:38 -0700 In-Reply-To: <20221104011041.290951-1-pcc@google.com> Message-Id: <20221104011041.290951-6-pcc@google.com> Mime-Version: 1.0 References: <20221104011041.290951-1-pcc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Subject: [PATCH v5 5/8] arm64: mte: Lock a page for MTE tag initialisation From: Peter Collingbourne To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Cc: Catalin Marinas , Cornelia Huck , Will Deacon , Marc Zyngier , Evgenii Stepanov , kvm@vger.kernel.org, Steven Price , Vincenzo Frascino , Peter Collingbourne X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221103_181113_850903_6D5E03A5 X-CRM114-Status: GOOD ( 27.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Catalin Marinas Initialising the tags and setting PG_mte_tagged flag for a page can race between multiple set_pte_at() on shared pages or setting the stage 2 pte via user_mem_abort(). Introduce a new PG_mte_lock flag as PG_arch_3 and set it before attempting page initialisation. Given that PG_mte_tagged is never cleared for a page, consider setting this flag to mean page unlocked and wait on this bit with acquire semantics if the page is locked: - try_page_mte_tagging() - lock the page for tagging, return true if it can be tagged, false if already tagged. No acquire semantics if it returns true (PG_mte_tagged not set) as there is no serialisation with a previous set_page_mte_tagged(). - set_page_mte_tagged() - set PG_mte_tagged with release semantics. The two-bit locking is based on Peter Collingbourne's idea. Signed-off-by: Catalin Marinas Signed-off-by: Peter Collingbourne Reviewed-by: Steven Price Cc: Will Deacon Cc: Marc Zyngier Cc: Peter Collingbourne Reviewed-by: Cornelia Huck --- arch/arm64/include/asm/mte.h | 35 +++++++++++++++++++++++++++++++- arch/arm64/include/asm/pgtable.h | 4 ++-- arch/arm64/kernel/cpufeature.c | 2 +- arch/arm64/kernel/mte.c | 12 +++-------- arch/arm64/kvm/guest.c | 16 +++++++++------ arch/arm64/kvm/mmu.c | 2 +- arch/arm64/mm/copypage.c | 2 ++ arch/arm64/mm/fault.c | 2 ++ arch/arm64/mm/mteswap.c | 14 +++++-------- 9 files changed, 60 insertions(+), 29 deletions(-) diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index 3f8199ba265a..20dd06d70af5 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -25,7 +25,7 @@ unsigned long mte_copy_tags_to_user(void __user *to, void *from, unsigned long n); int mte_save_tags(struct page *page); void mte_save_page_tags(const void *page_addr, void *tag_storage); -bool mte_restore_tags(swp_entry_t entry, struct page *page); +void mte_restore_tags(swp_entry_t entry, struct page *page); void mte_restore_page_tags(void *page_addr, const void *tag_storage); void mte_invalidate_tags(int type, pgoff_t offset); void mte_invalidate_tags_area(int type); @@ -36,6 +36,8 @@ void mte_free_tag_storage(char *storage); /* track which pages have valid allocation tags */ #define PG_mte_tagged PG_arch_2 +/* simple lock to avoid multiple threads tagging the same page */ +#define PG_mte_lock PG_arch_3 static inline void set_page_mte_tagged(struct page *page) { @@ -60,6 +62,33 @@ static inline bool page_mte_tagged(struct page *page) return ret; } +/* + * Lock the page for tagging and return 'true' if the page can be tagged, + * 'false' if already tagged. PG_mte_tagged is never cleared and therefore the + * locking only happens once for page initialisation. + * + * The page MTE lock state: + * + * Locked: PG_mte_lock && !PG_mte_tagged + * Unlocked: !PG_mte_lock || PG_mte_tagged + * + * Acquire semantics only if the page is tagged (returning 'false'). + */ +static inline bool try_page_mte_tagging(struct page *page) +{ + if (!test_and_set_bit(PG_mte_lock, &page->flags)) + return true; + + /* + * The tags are either being initialised or may have been initialised + * already. Check if the PG_mte_tagged flag has been set or wait + * otherwise. + */ + smp_cond_load_acquire(&page->flags, VAL & (1UL << PG_mte_tagged)); + + return false; +} + void mte_zero_clear_page_tags(void *addr); void mte_sync_tags(pte_t old_pte, pte_t pte); void mte_copy_page_tags(void *kto, const void *kfrom); @@ -86,6 +115,10 @@ static inline bool page_mte_tagged(struct page *page) { return false; } +static inline bool try_page_mte_tagging(struct page *page) +{ + return false; +} static inline void mte_zero_clear_page_tags(void *addr) { } diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index c6a2d8891d2a..c99fc9aec373 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1047,8 +1047,8 @@ static inline void arch_swap_invalidate_area(int type) #define __HAVE_ARCH_SWAP_RESTORE static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio) { - if (system_supports_mte() && mte_restore_tags(entry, &folio->page)) - set_page_mte_tagged(&folio->page); + if (system_supports_mte()) + mte_restore_tags(entry, &folio->page); } #endif /* CONFIG_ARM64_MTE */ diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index df11cfe61fcb..afb4ffd745c3 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2050,7 +2050,7 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) * Clear the tags in the zero page. This needs to be done via the * linear map which has the Tagged attribute. */ - if (!page_mte_tagged(ZERO_PAGE(0))) { + if (try_page_mte_tagging(ZERO_PAGE(0))) { mte_clear_page_tags(lm_alias(empty_zero_page)); set_page_mte_tagged(ZERO_PAGE(0)); } diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 84a085d536f8..f5bcb0dc6267 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -41,20 +41,14 @@ static void mte_sync_page_tags(struct page *page, pte_t old_pte, if (check_swap && is_swap_pte(old_pte)) { swp_entry_t entry = pte_to_swp_entry(old_pte); - if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) { - set_page_mte_tagged(page); - return; - } + if (!non_swap_entry(entry)) + mte_restore_tags(entry, page); } if (!pte_is_tagged) return; - /* - * Test PG_mte_tagged again in case it was racing with another - * set_pte_at(). - */ - if (!page_mte_tagged(page)) { + if (try_page_mte_tagging(page)) { mte_clear_page_tags(page_address(page)); set_page_mte_tagged(page); } diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 817fdd1ab778..5626ddb540ce 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -1068,15 +1068,19 @@ long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, clear_user(tags, MTE_GRANULES_PER_PAGE); kvm_release_pfn_clean(pfn); } else { + /* + * Only locking to serialise with a concurrent + * set_pte_at() in the VMM but still overriding the + * tags, hence ignoring the return value. + */ + try_page_mte_tagging(page); num_tags = mte_copy_tags_from_user(maddr, tags, MTE_GRANULES_PER_PAGE); - /* - * Set the flag after checking the write - * completed fully - */ - if (num_tags == MTE_GRANULES_PER_PAGE) - set_page_mte_tagged(page); + /* uaccess failed, don't leave stale tags */ + if (num_tags != MTE_GRANULES_PER_PAGE) + mte_clear_page_tags(page); + set_page_mte_tagged(page); kvm_release_pfn_dirty(pfn); } diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index e81bfb730629..fa2c85b93149 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1101,7 +1101,7 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn, return; for (i = 0; i < nr_pages; i++, page++) { - if (!page_mte_tagged(page)) { + if (try_page_mte_tagging(page)) { mte_clear_page_tags(page_address(page)); set_page_mte_tagged(page); } diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index 731d8a35701e..8dd5a8fe64b4 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -23,6 +23,8 @@ void copy_highpage(struct page *to, struct page *from) if (system_supports_mte() && page_mte_tagged(from)) { page_kasan_tag_reset(to); + /* It's a new page, shouldn't have been tagged yet */ + WARN_ON_ONCE(!try_page_mte_tagging(to)); mte_copy_page_tags(kto, kfrom); set_page_mte_tagged(to); } diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index e09e0344c7a7..0b1c102b89c9 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -937,6 +937,8 @@ struct page *alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma, void tag_clear_highpage(struct page *page) { + /* Newly allocated page, shouldn't have been tagged yet */ + WARN_ON_ONCE(!try_page_mte_tagging(page)); mte_zero_clear_page_tags(page_address(page)); set_page_mte_tagged(page); } diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index 70f913205db9..cd508ba80ab1 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -46,21 +46,17 @@ int mte_save_tags(struct page *page) return 0; } -bool mte_restore_tags(swp_entry_t entry, struct page *page) +void mte_restore_tags(swp_entry_t entry, struct page *page) { void *tags = xa_load(&mte_pages, entry.val); if (!tags) - return false; + return; - /* - * Test PG_mte_tagged again in case it was racing with another - * set_pte_at(). - */ - if (!test_and_set_bit(PG_mte_tagged, &page->flags)) + if (try_page_mte_tagging(page)) { mte_restore_page_tags(page_address(page), tags); - - return true; + set_page_mte_tagged(page); + } } void mte_invalidate_tags(int type, pgoff_t offset)