From patchwork Tue Jan 26 12:44:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: zhukeqian X-Patchwork-Id: 12046535 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 52FDAC433E9 for ; Tue, 26 Jan 2021 13:15:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 232BB2311D for ; Tue, 26 Jan 2021 13:15:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391739AbhAZNPX (ORCPT ); Tue, 26 Jan 2021 08:15:23 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:11503 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391789AbhAZMp6 (ORCPT ); Tue, 26 Jan 2021 07:45:58 -0500 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4DQ5yR1JhfzjDdq; Tue, 26 Jan 2021 20:43:59 +0800 (CST) Received: from DESKTOP-5IS4806.china.huawei.com (10.174.184.42) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.498.0; Tue, 26 Jan 2021 20:45:03 +0800 From: Keqian Zhu To: , , , , Marc Zyngier , Will Deacon , Catalin Marinas CC: Alex Williamson , Kirti Wankhede , Cornelia Huck , Mark Rutland , James Morse , Robin Murphy , Suzuki K Poulose , , , , , Subject: [RFC PATCH 2/7] kvm: arm64: Use atomic operation when update PTE Date: Tue, 26 Jan 2021 20:44:39 +0800 Message-ID: <20210126124444.27136-3-zhukeqian1@huawei.com> X-Mailer: git-send-email 2.8.4.windows.1 In-Reply-To: <20210126124444.27136-1-zhukeqian1@huawei.com> References: <20210126124444.27136-1-zhukeqian1@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.184.42] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org We are about to add HW_DBM support for stage2 dirty log, so software updating PTE may race with the MMU trying to set the access flag or dirty state. Use atomic oparations to avoid reverting these bits set by MMU. Signed-off-by: Keqian Zhu --- arch/arm64/kvm/hyp/pgtable.c | 41 ++++++++++++++++++++++++------------ 1 file changed, 27 insertions(+), 14 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index bdf8e55ed308..4915ba35f93b 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -153,10 +153,34 @@ static kvm_pte_t *kvm_pte_follow(kvm_pte_t pte) return __va(kvm_pte_to_phys(pte)); } +/* + * We may race with the MMU trying to set the access flag or dirty state, + * use atomic oparations to avoid reverting these bits. + * + * Return original PTE. + */ +static kvm_pte_t kvm_update_pte(kvm_pte_t *ptep, kvm_pte_t bit_set, + kvm_pte_t bit_clr) +{ + kvm_pte_t old_pte, pte = *ptep; + + do { + old_pte = pte; + pte &= ~bit_clr; + pte |= bit_set; + + if (old_pte == pte) + break; + + pte = cmpxchg_relaxed(ptep, old_pte, pte); + } while (pte != old_pte); + + return old_pte; +} + static void kvm_set_invalid_pte(kvm_pte_t *ptep) { - kvm_pte_t pte = *ptep; - WRITE_ONCE(*ptep, pte & ~KVM_PTE_VALID); + kvm_update_pte(ptep, 0, KVM_PTE_VALID); } static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp) @@ -723,18 +747,7 @@ static int stage2_attr_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, return 0; data->level = level; - data->pte = pte; - pte &= ~data->attr_clr; - pte |= data->attr_set; - - /* - * We may race with the CPU trying to set the access flag here, - * but worst-case the access flag update gets lost and will be - * set on the next access instead. - */ - if (data->pte != pte) - WRITE_ONCE(*ptep, pte); - + data->pte = kvm_update_pte(ptep, data->attr_set, data->attr_clr); return 0; }