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 144A2C433EF for ; Thu, 7 Jul 2022 17:04:02 +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-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=dgPSg1fVyCEW0ZsX89kQXlqp8y8WadQI/1znxUHuLdE=; b=oTIi+yfkVd37PK ByRxuvneezxOLKCSVgq8T7Btg1WTvSn6Iir7ACflizEdlK/5lHzYg/wiaDiQ2nXANFo29BYVWOtmn GvfKL/SnQccyIvPBkMvqz0ZPS2CsHKPvmST7L9ldsUtPaaWJXYgtQVLR23+l2ezSQQllOtVc5eWST w9+kbisX3OCGDMT53s5BAKNuqosYTvuMyOeCEzQnofVQCN3Zx1NveQQ6gs5ch7pD4suGitSbLuJ3d uRsIfT3lMS7lhcsYjNLMRl1/bMnyJvjk6wGbCWqWLv//M0dxTlIpPE9quP8ujJFftZE9i1DZcJK9j r6cfFe9HbsihQvV1Voqw==; 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Received: from 30.39.247.202(mailfrom:guanghuifeng@linux.alibaba.com fp:SMTPD_---0VIefA1B_1657213358) by smtp.aliyun-inc.com; Fri, 08 Jul 2022 01:02:40 +0800 Message-ID: Date: Fri, 8 Jul 2022 01:02:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation To: Catalin Marinas Cc: Mike Rapoport , Will Deacon , Ard Biesheuvel , baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com, james.morse@arm.com, quic_qiancai@quicinc.com, christophe.leroy@csgroup.eu, jonathan@marek.ca, mark.rutland@arm.com, thunder.leizhen@huawei.com, anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, geert+renesas@glider.be, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com References: <5d044fdd-a61a-d60f-d294-89e17de37712@linux.alibaba.com> <20220705121115.GB1012@willie-the-truck> <9974bea5-4db9-0104-c9c9-d9b49c390f1b@linux.alibaba.com> From: "guanghui.fgh" In-Reply-To: Content-Type: text/plain; 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b=ASFlSETqetSQ7CKLroanfiG7FmQF1cSbCwQ7THvUOPvUr8lCfuKp8wVvCgSg1+wGwQmAm6 8GklGDmKgWh+OPIf8IWlZiRmY0qsxlQRUMKOg1ocIJbUcnzMozvPL66+SdOz8Ax+0iNfiH jLPKiew8KpIsLgUs3OwzwrikZEQIV/I= Authentication-Results: imf28.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf28.hostedemail.com: domain of guanghuifeng@linux.alibaba.com designates 115.124.30.57 as permitted sender) smtp.mailfrom=guanghuifeng@linux.alibaba.com X-Stat-Signature: 43uu4j4g8kda4swr8u3kufn7sexj8i9w X-Rspamd-Queue-Id: 5494CC0065 X-Rspamd-Server: rspam05 X-Rspam-User: X-HE-Tag: 1657213364-960053 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Thanks. 在 2022/7/6 23:40, Catalin Marinas 写道: > On Wed, Jul 06, 2022 at 11:18:22PM +0800, guanghui.fgh wrote: >> 在 2022/7/6 21:54, Mike Rapoport 写道: >>> One thing I can think of is to only remap the crash kernel memory if it is >>> a part of an allocation that exactly fits into one ore more PUDs. >>> >>> Say, in reserve_crashkernel() we try the memblock_phys_alloc() with >>> PUD_SIZE as alignment and size rounded up to PUD_SIZE. If this allocation >>> succeeds, we remap the entire area that now contains only memory allocated >>> in reserve_crashkernel() and free the extra memory after remapping is done. >>> If the large allocation fails, we fall back to the original size and >>> alignment and don't allow unmapping crash kernel memory in >>> arch_kexec_protect_crashkres(). >> >> There is a new method. >> I think we should use the patch v3(similar but need add some changes) >> >> 1.We can walk crashkernle block/section pagetable, >> [[[(keep the origin block/section mapping valid]]] >> rebuild the pte level page mapping for the crashkernel mem >> rebuild left & right margin mem(which is in same block/section mapping but >> out of crashkernel mem) with block/section mapping >> >> 2.'replace' the origin block/section mapping by new builded mapping >> iterately >> >> With this method, all the mem mapping keep valid all the time. > > As I already commented on one of your previous patches, this is not > allowed by the architecture. If FEAT_BBM is implemented (ARMv8.4 I > think), the worst that can happen is a TLB conflict abort and the > handler should invalidate the TLBs and restart the faulting instruction, > assuming the handler won't try to access the same conflicting virtual > address. Prior to FEAT_BBM, that's not possible as the architecture does > not describe a precise behaviour of conflicting TLB entries (you might > as well get the TLB output of multiple entries being or'ed together). > I think there is another way to handle it. 1.We can rebuild the crashkernel mem mapping firstly, but [[[don't change the origin linear mapping]]]. 2.Afterward, we can reuse the idmap_pg_dir and switch to it. We use idmap_pg_dir to change the linear mapping which complyes with the TLB BBM.