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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 185FDC43334 for ; Mon, 18 Jul 2022 13:10:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A9AA56B0072; Mon, 18 Jul 2022 09:10:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A49996B0073; Mon, 18 Jul 2022 09:10:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 93AB96B0074; Mon, 18 Jul 2022 09:10:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 83AC16B0072 for ; Mon, 18 Jul 2022 09:10:18 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 5EC8776D for ; Mon, 18 Jul 2022 13:10:18 +0000 (UTC) X-FDA: 79700254116.10.7B9974F Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf28.hostedemail.com (Postfix) with ESMTP id E6A49C0071 for ; Mon, 18 Jul 2022 13:10:17 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E3805B81609; Mon, 18 Jul 2022 13:10:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B5FA2C341C0; Mon, 18 Jul 2022 13:10:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658149814; bh=hdsWoAacUlbtUsKYM7Fe7L2NSapcAMw6cTP36dELNto=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GwA3mNLUulPloNbONSLsDZACF7hUfHV0fY4DrHU2VveDdLJvhRLg9RbKosmmiafZD 9Hqc2ojdFd9zgs4/Ff60q8fScSFzEE01jLqAY5PK3S4+hkNlZ8Ynvq4XzG2Ls5guLs gUQSS68IB9XNiYxkciO64glvbjEp0oEm9JgC/DRbnHIPb/1m7tNoo8W8xJfXke3voe P4LlRmVDgwWXqWjKqECUV/0jeYRvd8nL8hOSb1juhn8wx5PCPwdf1WGik3UkzyWtkn UeA+VqLF70nrSe+WsDuMlkv+swx9Wd1x24x/8/8ZP6X59996uWI9FMq+HH+v28Y2f8 Q8ScC2k+QkHFw== Date: Mon, 18 Jul 2022 14:10:06 +0100 From: Will Deacon To: "guanghui.fgh" Cc: baolin.wang@linux.alibaba.com, catalin.marinas@arm.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, rppt@kernel.org, geert+renesas@glider.be, ardb@kernel.org, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com Subject: Re: [PATCH v5] arm64: mm: fix linear mem mapping access performance degradation Message-ID: <20220718131005.GA12406@willie-the-truck> References: <1657460657-25698-1-git-send-email-guanghuifeng@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658149818; a=rsa-sha256; cv=none; b=VnmyPghrFypC+Q7HWPhLIpZTvIR2fn4W/uOVeV8xcTogNSr5mQTSQD2sGa2hdBG6UoS/JJ xMyE56jEAAXcoD3LGsPh7db/kN57Kn6LgPKPSPan71LKgriM+cyx+85AHDvhJMbW13IISN ZX38WraHk/eeJlMrtCrYkqbOu1aJ/fs= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GwA3mNLU; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf28.hostedemail.com: domain of will@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=will@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658149818; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=LySHogeRoblek8pVB8mYMEYaHGhf0dTviB+fXwId8PY=; b=zSZ4OlBCsi96rkvp18M/HImm2Yf6C1r2SyEea4zGxBKkUha3tc9oAWnwwbjQ7vKJFTeCSx szJDpMg3KppnAWA8TngdntnzLcyiH9N1VbMLaCBtBBv8Taozf4q51rc+sux/R1BfEv9xxb xYfE9vvaVXqd7Bymj9Xqnfv5jNQJqHA= X-Stat-Signature: xdknxgugp5sa5kbfi3tmqeqoz7ijuowb X-Rspamd-Queue-Id: E6A49C0071 Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GwA3mNLU; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf28.hostedemail.com: domain of will@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=will@kernel.org X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1658149817-235476 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: On Sun, Jul 10, 2022 at 11:33:02PM +0800, guanghui.fgh wrote: > In short, this path work: > > 1.Before doing work for rebuiling crashkernel mem, the pgd is swapper_pg_dir > in [[[ttbr1]]] > > 2.Change the [[[ttbr0]]]to use idmap_pg_dir pgd > > 3.The [[[idmap_cpu_replace_ttbr1_with_flush_tlb]]] are mapped [[[only]]] > with idmap_pg_dir mapping in [[[ttbr0]]] > > 4.The [[[idmap_cpu_replace_ttbr1_with_flush_tlb]]] will flush tlb all, > switch [[[ttbr1]]] to use init_pg_dir pgd(and flush tlb all again). > There is no tlb conflict to swapper_pg_dir. > There is no tlb cache for swapper_pg_dir. > > 5.Woring with init_pg_dir pgd to access swapper_pg_dir pagetable with fix > mapping. And modify crashkernel mapping in the swapper_pg_dir without any > tlb conflict and flush. > > 6.When finishing the work, switch ttbr1 pgd to the origin swapper_pg_dir > with cpu_replace_ttbr1 function(similar to the above). I do not think that this complexity is justified. As I have stated on numerous occasions already, I would prefer that we leave the crashkernel mapped when rodata is not "full". That fixes your performance issue and matches what we do for module code, so I do not see a security argument against it. I do not plan to merge this patch as-is. Thanks, Will