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=-15.2 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_SANE_1 autolearn=unavailable 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 49E9AC433ED for ; Wed, 19 May 2021 18:06:24 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 96399611BD for ; Wed, 19 May 2021 18:06:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96399611BD 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 29CEE4B3AC; Wed, 19 May 2021 14:06:23 -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 3kUQD7+e+clX; Wed, 19 May 2021 14:06:21 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 106FC4B847; Wed, 19 May 2021 14:06:21 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id DFE874B83C for ; Wed, 19 May 2021 14:06:19 -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 wE1Mp6IKtMyD for ; Wed, 19 May 2021 14:06:18 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id A7DA74B3AC for ; Wed, 19 May 2021 14:06:18 -0400 (EDT) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9D76D611BF; Wed, 19 May 2021 18:06:13 +0000 (UTC) Date: Wed, 19 May 2021 19:06:10 +0100 From: Catalin Marinas To: Steven Price Subject: Re: [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Message-ID: <20210519180610.GE21619@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-4-steven.price@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210517123239.8025-4-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: "Dr. David Alan Gilbert" , qemu-devel@nongnu.org, Marc Zyngier , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu 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 On Mon, May 17, 2021 at 01:32:34PM +0100, 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 for which pte_access_permitted() returns false > as these will not have been swapped out. > > Signed-off-by: Steven Price > --- > arch/arm64/include/asm/pgtable.h | 9 +++++++-- > arch/arm64/kernel/mte.c | 16 ++++++++++++++-- > 2 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0b10204e72fc..275178a810c1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -314,8 +314,13 @@ 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)) > + /* > + * If the PTE would provide user space access to the tags associated > + * with it then ensure that the MTE tags are synchronised. Exec-only > + * mappings don't expose tags (instruction fetches don't check tags). > + */ > + if (system_supports_mte() && pte_present(pte) && > + pte_access_permitted(pte, false) && !pte_special(pte)) > mte_sync_tags(ptep, pte); Looking at the mte_sync_page_tags() logic, we bail out early if it's the old pte is not a swap one and the new pte is not tagged. So we only need to call mte_sync_tags() if it's a tagged new pte or the old one is swap. What about changing the set_pte_at() test to: if (system_supports_mte() && pte_present(pte) && !pte_special(pte) && (pte_tagged(pte) || is_swap_pte(READ_ONCE(*ptep)))) mte_sync_tags(ptep, pte); We can even change mte_sync_tags() to take the old pte directly: if (system_supports_mte() && pte_present(pte) && !pte_special(pte)) { pte_t old_pte = READ_ONCE(*ptep); if (pte_tagged(pte) || is_swap_pte(old_pte)) mte_sync_tags(old_pte, pte); } It would save a function call in most cases where the page is not tagged. -- Catalin _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-15.6 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=unavailable 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 2CD89C433ED for ; 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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 Mon, May 17, 2021 at 01:32:34PM +0100, 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 for which pte_access_permitted() returns false > as these will not have been swapped out. > > Signed-off-by: Steven Price > --- > arch/arm64/include/asm/pgtable.h | 9 +++++++-- > arch/arm64/kernel/mte.c | 16 ++++++++++++++-- > 2 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0b10204e72fc..275178a810c1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -314,8 +314,13 @@ 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)) > + /* > + * If the PTE would provide user space access to the tags associated > + * with it then ensure that the MTE tags are synchronised. Exec-only > + * mappings don't expose tags (instruction fetches don't check tags). > + */ > + if (system_supports_mte() && pte_present(pte) && > + pte_access_permitted(pte, false) && !pte_special(pte)) > mte_sync_tags(ptep, pte); Looking at the mte_sync_page_tags() logic, we bail out early if it's the old pte is not a swap one and the new pte is not tagged. So we only need to call mte_sync_tags() if it's a tagged new pte or the old one is swap. What about changing the set_pte_at() test to: if (system_supports_mte() && pte_present(pte) && !pte_special(pte) && (pte_tagged(pte) || is_swap_pte(READ_ONCE(*ptep)))) mte_sync_tags(ptep, pte); We can even change mte_sync_tags() to take the old pte directly: if (system_supports_mte() && pte_present(pte) && !pte_special(pte)) { pte_t old_pte = READ_ONCE(*ptep); if (pte_tagged(pte) || is_swap_pte(old_pte)) mte_sync_tags(old_pte, pte); } It would save a function call in most cases where the page is not tagged. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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=-15.2 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_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 D40CAC433ED for ; Wed, 19 May 2021 18:06:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B068361355 for ; Wed, 19 May 2021 18:06:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231173AbhESSHh (ORCPT ); Wed, 19 May 2021 14:07:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:33646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230023AbhESSHg (ORCPT ); Wed, 19 May 2021 14:07:36 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9D76D611BF; Wed, 19 May 2021 18:06:13 +0000 (UTC) Date: Wed, 19 May 2021 19:06:10 +0100 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 v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Message-ID: <20210519180610.GE21619@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-4-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210517123239.8025-4-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 17, 2021 at 01:32:34PM +0100, 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 for which pte_access_permitted() returns false > as these will not have been swapped out. > > Signed-off-by: Steven Price > --- > arch/arm64/include/asm/pgtable.h | 9 +++++++-- > arch/arm64/kernel/mte.c | 16 ++++++++++++++-- > 2 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0b10204e72fc..275178a810c1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -314,8 +314,13 @@ 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)) > + /* > + * If the PTE would provide user space access to the tags associated > + * with it then ensure that the MTE tags are synchronised. Exec-only > + * mappings don't expose tags (instruction fetches don't check tags). > + */ > + if (system_supports_mte() && pte_present(pte) && > + pte_access_permitted(pte, false) && !pte_special(pte)) > mte_sync_tags(ptep, pte); Looking at the mte_sync_page_tags() logic, we bail out early if it's the old pte is not a swap one and the new pte is not tagged. So we only need to call mte_sync_tags() if it's a tagged new pte or the old one is swap. What about changing the set_pte_at() test to: if (system_supports_mte() && pte_present(pte) && !pte_special(pte) && (pte_tagged(pte) || is_swap_pte(READ_ONCE(*ptep)))) mte_sync_tags(ptep, pte); We can even change mte_sync_tags() to take the old pte directly: if (system_supports_mte() && pte_present(pte) && !pte_special(pte)) { pte_t old_pte = READ_ONCE(*ptep); if (pte_tagged(pte) || is_swap_pte(old_pte)) mte_sync_tags(old_pte, pte); } It would save a function call in most cases where the page is not tagged. -- Catalin 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=-15.2 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_SANE_1 autolearn=unavailable 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 589ABC433B4 for ; Wed, 19 May 2021 18:07:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 BF28761244 for ; Wed, 19 May 2021 18:07:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF28761244 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35158 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ljQbl-0001Pv-O7 for qemu-devel@archiver.kernel.org; Wed, 19 May 2021 14:07:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40766) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ljQaM-0000QT-LH for qemu-devel@nongnu.org; Wed, 19 May 2021 14:06:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:50584) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ljQaK-0001NP-1V for qemu-devel@nongnu.org; Wed, 19 May 2021 14:06:22 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9D76D611BF; Wed, 19 May 2021 18:06:13 +0000 (UTC) Date: Wed, 19 May 2021 19:06:10 +0100 From: Catalin Marinas To: Steven Price Subject: Re: [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Message-ID: <20210519180610.GE21619@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-4-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210517123239.8025-4-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Received-SPF: pass client-ip=198.145.29.99; envelope-from=cmarinas@kernel.org; helo=mail.kernel.org X-Spam_score_int: -66 X-Spam_score: -6.7 X-Spam_bar: ------ X-Spam_report: (-6.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_HI=-5, 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, Marc Zyngier , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , James Morse , linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, May 17, 2021 at 01:32:34PM +0100, 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 for which pte_access_permitted() returns false > as these will not have been swapped out. > > Signed-off-by: Steven Price > --- > arch/arm64/include/asm/pgtable.h | 9 +++++++-- > arch/arm64/kernel/mte.c | 16 ++++++++++++++-- > 2 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0b10204e72fc..275178a810c1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -314,8 +314,13 @@ 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)) > + /* > + * If the PTE would provide user space access to the tags associated > + * with it then ensure that the MTE tags are synchronised. Exec-only > + * mappings don't expose tags (instruction fetches don't check tags). > + */ > + if (system_supports_mte() && pte_present(pte) && > + pte_access_permitted(pte, false) && !pte_special(pte)) > mte_sync_tags(ptep, pte); Looking at the mte_sync_page_tags() logic, we bail out early if it's the old pte is not a swap one and the new pte is not tagged. So we only need to call mte_sync_tags() if it's a tagged new pte or the old one is swap. What about changing the set_pte_at() test to: if (system_supports_mte() && pte_present(pte) && !pte_special(pte) && (pte_tagged(pte) || is_swap_pte(READ_ONCE(*ptep)))) mte_sync_tags(ptep, pte); We can even change mte_sync_tags() to take the old pte directly: if (system_supports_mte() && pte_present(pte) && !pte_special(pte)) { pte_t old_pte = READ_ONCE(*ptep); if (pte_tagged(pte) || is_swap_pte(old_pte)) mte_sync_tags(old_pte, pte); } It would save a function call in most cases where the page is not tagged. -- Catalin