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=-15.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 1788BC433C1 for ; Fri, 26 Mar 2021 18:58:24 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 96A0B61A02 for ; Fri, 26 Mar 2021 18:58:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96A0B61A02 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; 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=pjW1K4s3OYD2hDP4P3oHSV9RvvM9FsGnuqhW5wzgW5o=; b=McBcteVBCJIsJbpvh4hr0ZyNF CmEVv+CPMDNAjh2niHNbrnaTkpEg4oI87F+gJWNpqYqUQ4HqMQRymkYvw8VL7mEzpJT2JUWtetudI ZzOnzYrmwWqE1Oih0NVmlbqZ55B/BCypDkf/OJ2mVMnKur33ju7ld7yTKSPoF+CnnR/vvaCuobXOv TTwjSS83EjJt95XpoV6MJp+M3mtCoYEGYE+ddYD2QUWqmmGxqjSDfqc+GARoeiGj7QiGLkBVJtWeu Hd8+an1ALjoAkeXM9O7sCMTcHx9/FjF3sviYf0Fwv6DzRrEmWH3EcbOCvFzShZmdHyjkJoS5waBhP XkxkIGBBA==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lPrdp-004Aaz-GI; Fri, 26 Mar 2021 18:57:05 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lPrdl-004Aa4-Hg for linux-arm-kernel@lists.infradead.org; Fri, 26 Mar 2021 18:57:03 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F6AA619F7; Fri, 26 Mar 2021 18:56:56 +0000 (UTC) Date: Fri, 26 Mar 2021 18:56:54 +0000 From: Catalin Marinas To: Steven Price Cc: Marc Zyngier , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: Re: [PATCH v10 1/6] arm64: mte: Sync tags for pages where PTE is untagged Message-ID: <20210326185653.GG5126@arm.com> References: <20210312151902.17853-1-steven.price@arm.com> <20210312151902.17853-2-steven.price@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210312151902.17853-2-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210326_185701_805642_DDA3F564 X-CRM114-Status: GOOD ( 19.87 ) 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 Hi Steven, On Fri, Mar 12, 2021 at 03:18:57PM +0000, Steven Price wrote: > 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 which are !pte_valid_user() as these will > not have been swapped out. > > Signed-off-by: Steven Price > --- > arch/arm64/include/asm/pgtable.h | 2 +- > arch/arm64/kernel/mte.c | 16 ++++++++++++---- > 2 files changed, 13 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index e17b96d0e4b5..84166625c989 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, > __sync_icache_dcache(pte); > > if (system_supports_mte() && > - pte_present(pte) && pte_tagged(pte) && !pte_special(pte)) > + pte_present(pte) && pte_valid_user(pte) && !pte_special(pte)) > mte_sync_tags(ptep, pte); With the EPAN patches queued in for-next/epan, pte_valid_user() disappeared as its semantics weren't very clear. So this relies on the set_pte_at() being done on the VMM address space. I wonder, if the VMM did an mprotect(PROT_NONE), can the VM still access it via stage 2? If yes, the pte_valid_user() test wouldn't work. We need something like pte_present() && addr <= user_addr_max(). BTW, ignoring virtualisation, can we ever bring a page in from swap on a PROT_NONE mapping (say fault-around)? It's not too bad if we keep the metadata around for when the pte becomes accessible but I suspect we remove it if the page is removed from swap. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel