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 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 684F9ECAAD5 for ; Fri, 2 Sep 2022 16:59:36 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=gzEbT6oK7x9B1Y8Zb2NsnrbRvmSOAOvcFj32Fom2H8s=; b=nPMx8xczYN1hoE dfSfFgugC8fsMq/wTSUSnLBMkiZqpqdvlrr/S/kDwOR7XbFlASAizOHNZP6MvMl1i3LDibRsmmdix YrUL+cy3FSVOEboMoAWQqwliboywkUcNx/7NQFHY3wD74YOVVfIYQ3V3DY488NNPPHr+Z3hijHki2 /aQ7dwj6oISSr8pP48jqU0aVFSYhd0Bm5bIubQ+p1BnaPezi7s1UuTOMwciZbYV1UwFQl+vu2vT7J 25II7FISj+bDAn1u4KO9Q9iWTL5y4wL0BGHE2sQB/lwv8MfwDgNB6dMfXrFVOaO1Zk3RSNRcoDbHN 8TGNaPbpwRnUXLneolGQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oU9zz-007YBf-5Z; Fri, 02 Sep 2022 16:58:31 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oU9zv-007Y4I-I2 for linux-arm-kernel@lists.infradead.org; Fri, 02 Sep 2022 16:58:29 +0000 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 ams.source.kernel.org (Postfix) with ESMTPS id 14194B82CCA; Fri, 2 Sep 2022 16:58:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDA65C433D7; Fri, 2 Sep 2022 16:58:22 +0000 (UTC) Date: Fri, 2 Sep 2022 17:58:19 +0100 From: Catalin Marinas To: Steven Price Cc: Peter Collingbourne , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, Cornelia Huck , Will Deacon , Marc Zyngier , Evgenii Stepanov , kvm@vger.kernel.org, Vincenzo Frascino Subject: Re: [PATCH v3 4/7] arm64: mte: Lock a page for MTE tag initialisation Message-ID: References: <20220810193033.1090251-1-pcc@google.com> <20220810193033.1090251-5-pcc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220902_095827_890415_F5F5770D X-CRM114-Status: GOOD ( 23.84 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 02, 2022 at 05:28:47PM +0100, Catalin Marinas wrote: > On Fri, Sep 02, 2022 at 03:47:33PM +0100, Steven Price wrote: > > On 10/08/2022 20:30, Peter Collingbourne wrote: > > > diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c > > > index a78c1db23c68..cd5ad0936e16 100644 > > > --- a/arch/arm64/mm/mteswap.c > > > +++ b/arch/arm64/mm/mteswap.c > > > @@ -53,6 +53,9 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page) > > > if (!tags) > > > return false; > > > > > > + /* racing tag restoring? */ > > > + if (!try_page_mte_tagging(page)) > > > + return false; > > > mte_restore_page_tags(page_address(page), tags); > > > > I feel like adding a "set_page_mte_tagged(page);" in here would avoid > > the need for the comments about mte_restore_tags() taking the lock. > > Good point. I think I blindly followed the set_bit() places but it makes > sense to move the bit setting to mte_restore_tags(). Something like this (and I need to do some more testing): diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index b956899467f0..be6560e1ff2b 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); diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e6b82ad1e9e6..7d91379382fd 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1049,9 +1049,8 @@ 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) { - /* mte_restore_tags() takes the PG_mte_lock */ - 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/mte.c b/arch/arm64/kernel/mte.c index 634e089b5933..54ab6c4741db 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -41,11 +41,8 @@ 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); - /* mte_restore_tags() takes the PG_mte_lock */ - 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) diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index cd5ad0936e16..cd508ba80ab1 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -46,19 +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; - /* racing tag restoring? */ - if (!try_page_mte_tagging(page)) - return false; - mte_restore_page_tags(page_address(page), tags); - - return true; + if (try_page_mte_tagging(page)) { + mte_restore_page_tags(page_address(page), tags); + set_page_mte_tagged(page); + } } void mte_invalidate_tags(int type, pgoff_t offset) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel