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=-15.7 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,NICE_REPLY_A,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 19DEDC433E0 for ; Thu, 14 Jan 2021 09:30:21 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 BFD9023A04 for ; Thu, 14 Jan 2021 09:30:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFD9023A04 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.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=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=aIkFjsvz9ERd+XlrroGLo9AOHKstOYSEjZiWprw9f90=; b=sqArwdeg48wX6FidoGs7KQvgq o9JzpGtprRkiC2rs2B8Grh1gbsy+1ztn4D8+yxSESdSiGCoaLGIXIqLoyfbfRZ1GBP6YiufeAQCv0 vUSXeABaI+VrYCYXl//p4m3Imw5e2xcrvCbCMTMrnE8yV9LQxXlZ4tyid0JU/Km2/JZnosuqeiwdn bMQawKSxvkm5EtDoj4fWvBdwcPs5O+RlRfKqGaQKoMSP0KxvV/wFMDTiF5cCyMJbCRS1XkJyUblly cMo7afOQOrSVid3pS5TkpYdJvY+XDqKVlRbdNwfAOLwM7L5cvUbglD6bvtkNx2m+DTQcuq8LLgpbT /mO5n/E9Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kzyvX-0004k5-Ja; Thu, 14 Jan 2021 09:28:23 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kzyvT-0004h9-Fc for linux-arm-kernel@lists.infradead.org; Thu, 14 Jan 2021 09:28:22 +0000 Received: from dggeme763-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4DGf8y6R29zXyj9; Thu, 14 Jan 2021 17:27:14 +0800 (CST) Received: from [10.174.187.128] (10.174.187.128) by dggeme763-chm.china.huawei.com (10.3.19.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Thu, 14 Jan 2021 17:28:09 +0800 Subject: Re: [PATCH v2 2/3] KVM: arm64: Add prejudgement for relaxing permissions only case in stage2 translation fault handler To: Will Deacon References: <20201216122844.25092-1-wangyanan55@huawei.com> <20201216122844.25092-3-wangyanan55@huawei.com> <20210113154414.GA11892@willie-the-truck> From: "wangyanan (Y)" Message-ID: Date: Thu, 14 Jan 2021 17:28:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20210113154414.GA11892@willie-the-truck> Content-Language: en-US X-Originating-IP: [10.174.187.128] X-ClientProxiedBy: dggeme702-chm.china.huawei.com (10.1.199.98) To dggeme763-chm.china.huawei.com (10.3.19.109) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210114_042821_256307_95828B16 X-CRM114-Status: GOOD ( 18.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gavin Shan , Suzuki K Poulose , Marc Zyngier , Quentin Perret , linux-kernel@vger.kernel.org, yezengruan@huawei.com, James Morse , linux-arm-kernel@lists.infradead.org, Catalin Marinas , yuzenghui@huawei.com, wanghaibin.wang@huawei.com, zhukeqian1@huawei.com, Julien Thierry Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2021/1/13 23:44, Will Deacon wrote: > On Wed, Dec 16, 2020 at 08:28:43PM +0800, Yanan Wang wrote: >> In dirty-logging, or dirty-logging-stopped time, even normal running >> time of a guest configed with huge mappings and numbers of vCPUs, >> translation faults by different vCPUs on the same GPA could occur >> successively almost at the same time. There are two reasons for it. >> >> (1) If there are some vCPUs accessing the same GPA at the same time and >> the leaf PTE is not set yet, then they will all cause translation faults >> and the first vCPU holding mmu_lock will set valid leaf PTE, and the >> others will later update the old PTE with a new one if they are different. >> >> (2) When changing a leaf entry or a table entry with break-before-make, >> if there are some vCPUs accessing the same GPA just catch the moment when >> the target PTE is set invalid in a BBM procedure coincidentally, they will >> all cause translation faults and will later update the old PTE with a new >> one if they are different. >> >> The worst case can be like this: vCPU A causes a translation fault with RW >> prot and sets the leaf PTE with RW permissions, and then the next vCPU B >> with RO prot updates the PTE back to RO permissions with break-before-make. >> And the BBM-invalid moment may trigger more unnecessary translation faults, >> then some useless small loops might occur which could lead to vCPU stuck. >> >> To avoid unnecessary update and small loops, add prejudgement in the >> translation fault handler: Skip updating the PTE with break-before-make >> if we are trying to recreate the exact same mapping or only change the >> access permissions. Actually, change of permissions will be handled >> through the relax_perms path next time if necessary. >> >> Signed-off-by: Yanan Wang >> --- >> arch/arm64/kvm/hyp/pgtable.c | 28 +++++++++++++++++++--------- >> 1 file changed, 19 insertions(+), 9 deletions(-) >> >> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c >> index 350f9f810930..8225ced49bad 100644 >> --- a/arch/arm64/kvm/hyp/pgtable.c >> +++ b/arch/arm64/kvm/hyp/pgtable.c >> @@ -45,6 +45,10 @@ >> >> #define KVM_PTE_LEAF_ATTR_HI_S2_XN BIT(54) >> >> +#define KVM_PTE_LEAF_ATTR_S2_PERMS (KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \ >> + KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \ >> + KVM_PTE_LEAF_ATTR_HI_S2_XN) >> + >> struct kvm_pgtable_walk_data { >> struct kvm_pgtable *pgt; >> struct kvm_pgtable_walker *walker; >> @@ -460,7 +464,7 @@ static int stage2_map_set_prot_attr(enum kvm_pgtable_prot prot, >> return 0; >> } >> >> -static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, >> +static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, >> kvm_pte_t *ptep, >> struct stage2_map_data *data) >> { >> @@ -469,13 +473,18 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, >> struct page *page = virt_to_page(ptep); >> >> if (!kvm_block_mapping_supported(addr, end, phys, level)) >> - return false; >> + return 1; > It would probably be cleaner to return another error code here, as we > have failed to install a mapping (e.g. E2BIG or perhaps more perversely, > ENOTBLK). Then the caller can decide to install a trable. > Ok, I will make some adjustment for this and post the v3 soon after. Thanks, Yanan. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel