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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 830B0C433DF for ; Wed, 22 Jul 2020 20:22:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6644B20684 for ; Wed, 22 Jul 2020 20:22:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732566AbgGVUWp (ORCPT ); Wed, 22 Jul 2020 16:22:45 -0400 Received: from mout.kundenserver.de ([217.72.192.75]:42915 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726447AbgGVUWo (ORCPT ); Wed, 22 Jul 2020 16:22:44 -0400 Received: from mail-qt1-f181.google.com ([209.85.160.181]) by mrelayeu.kundenserver.de (mreue108 [212.227.15.145]) with ESMTPSA (Nemesis) id 1N7zNt-1kuHVR43Kl-0155Dj for ; Wed, 22 Jul 2020 22:22:43 +0200 Received: by mail-qt1-f181.google.com with SMTP id 6so2863990qtt.0 for ; Wed, 22 Jul 2020 13:22:42 -0700 (PDT) X-Gm-Message-State: AOAM530fNPwjI9AXsKOAxR+2uVFb/GvVoTmCYJXVEyxb4ebysTSew3Lp ejnmMiMCvQt9Cnc8dL6vDGjqXZgafUTH3F9aqYo= X-Google-Smtp-Source: ABdhPJzomOuvyv87HLrmnRqLMg+xagc+vFRLOHIlCjUhIO6Ps1D+MblDa1Ac6NHH61/GfVpqpoR58oXKvv+qOpTZNZk= X-Received: by 2002:ac8:6743:: with SMTP id n3mr1132159qtp.7.1595449361849; Wed, 22 Jul 2020 13:22:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Arnd Bergmann Date: Wed, 22 Jul 2020 22:22:25 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone To: Palmer Dabbelt Cc: Alexandre Ghiti , Albert Ou , Benjamin Herrenschmidt , Linux-MM , Michael Ellerman , Anup Patel , "linux-kernel@vger.kernel.org" , Atish Patra , Paul Mackerras , Zong Li , Paul Walmsley , linux-riscv , linuxppc-dev Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:9vkYCDJmvYwb5URpXaDM+la+4kepzavYjlt9hqPnJqKRPI6eKW4 6sOsFIFn47uxY38ztrWUjk+xfOcR6ptqSoEXhVkEUQ95MTZSyMYjog/VrxLAss+sy+xZAJu OKVnQnjmtC2vXaYoPglA5FmuqqaxXSM0ZG1gD/DWvFpv4sAcMnEPhR/6dfk6ZNqTACYr754 kubdmpCEKhXU1sID7DJHw== X-UI-Out-Filterresults: notjunk:1;V03:K0:BeYHuheCQD0=:GD9dn33K3tWuL2rvUuTamS DPkvmv3u8jAJtJPpBDP+bjHIJVmx3B6N4Kx2Iy9paj9y82diPWi4pKEVCofWY4oT/OMq22sf3 Qq0BmjyRe6SdpDwH2oBDGoK/XlwN6hoKuZNihDYjUwFz0Tkz5q9eW124hjEVcifytBL4wOgWh Y0ui8xsROECASvu0nlaJq47SqC3w3/ZcwAV5jV44m1OPK2u2UO3lksgYM/U7mTdSlyZ/76Kua rsjtrZ3292bW5ZR8cwIzblbwZzHFT0BFx6/ymiDkdNCQr7OEqG+CHUwd4OeJEGKMRymBhnS2x qz1RtRIHDHXWRwBwJGkN/eefVo3mZp2L2Jz66anFFP/lXy/OCV5B/1OUGwY5qBNry23dM3/eI RvOEMgjmEjpYtDM0dVhIQ/U8uIc/OD1MZdto6TtrSQuOeGcVKU+yEJ4JdX/xmobCUii8t45ys NIkFaMhbnk5rKv/ERiuHszJfvGvKiBlBqSppadT1kmAxE+20SUY8S+mUwodcVFsYhata31Eg1 1pTD3JNXXMO4cxyqSdxk5BDndXbsbWqiKt8tek6CSJIViO05fJsnkZVIkOAwoIloT1h3F4FdS Z5Lee1BNuWnFkAwLoDLn91fggX8olfJHRK4gkBUQydR4BjBrfzxmh7u9Ov2a8R1v/EjYYxakJ piv5LrybbJi8odnVryKx3MA8tByKE1FCd6eZfRyzsr22EAglXSGQmIg4FQKbz/d+UhlQDUj5z ukwmSK2NrcYeJFnfu/4SnL2LP4Ar9EIfNFQsrdewCr1GnrtiU21JS2PeWP2h9PXdunZQnKe6i ob4gJ6G8w4V4mqFV/ljF0rXzcgQdujBVGsirFEcer2WeuSwTI/SFC9KW+psS/vYfJlRkImj Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > The eventual goal is to have a split of 3840MB for either user or linear map > > plus and 256MB for vmalloc, including the kernel. Switching between linear > > and user has a noticeable runtime overhead, but it relaxes both the limits > > for user memory and lowmem, and it provides a somewhat stronger > > address space isolation. > > Ya, I think we decided not to do that, at least for now. I guess the right > answer there will depend on what 32-bit systems look like, and since we don't > have any I'm inclined to just stick to the fast option. Makes sense. Actually on 32-bit Arm we see fewer large-memory configurations in new machines than we had in the past before 64-bit machines were widely available at low cost, so I expect not to see a lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips) for cost reasons, and rv32 is likely going to be similar, so you may never really see a need for highmem or the above hack to increase the size of the linear mapping. I just noticed that rv32 allows 2GB of lowmem rather than just the usual 768MB or 1GB, at the expense of addressable user memory. This seems like an unusual choice, but I also don't see any reason to change this or make it more flexible unless actual users appear. Arnd 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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 51E9CC433E4 for ; Wed, 22 Jul 2020 20:23:01 +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 1CAED20684 for ; Wed, 22 Jul 2020 20:23:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="wropAYmd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1CAED20684 Authentication-Results: mail.kernel.org; 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Wed, 22 Jul 2020 13:22:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Arnd Bergmann Date: Wed, 22 Jul 2020 22:22:25 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone To: Palmer Dabbelt X-Provags-ID: V03:K1:J8ck2IcelAMzGc53QPdXUblwo//9C65t+/ud5oyCvtjfg/JA3Dv OZwmYNVHGMAHDEYnnD1g238AV+O01f08cQk4ZP3kMlQAJOAcyHSdO+rAwp2Xsw+geDjINdI a5mDLdsSVNurlqmURYZoB6ha0N0+ZtqJiU/YzCIEZrKRmAFYAR0RDRi1JZIINByvcWHauAf 0xFpnjL1XZf0SDjDNc7qg== X-UI-Out-Filterresults: notjunk:1;V03:K0:dBmn0ZZNjdY=:BcSKhULG0M4xE8aaAR1tn2 VNKZQtxMm/ELcF8HecKBkw58W7Q+uQbx3X0ynJ6a2Fe47VzzVmQxyWg8509nNkJAH1iFuRK0R ZPtzJvGxuRivn/iQAsgVX1WSwHPEAr9XhWtpLlMMsT/G66UvBSvKQ0M8Inr0OQDenEyWw49XP A1tTZmAjhDDD5bP/Nvib5qATauzt03TFfYn3DhAV6L+6Q0Z+37hTEJeLDmjSnO+n+CXIBm5P9 4ZkcQgWffQ0U3D5WeXyQsqc4pq1M3nVoknz5zBYjPkAyqzF08WLInS4t7TFaba11xqnnxyrpq fjJAzRGMScDpLUNwsNXnvRZZ6Cd/MeMWvwabsntMUMGyp7T8Eryv5bPkPWCFdoifT5qZzxKed SYmidNcxvp6Q0QblzuPTZIVC71QE6Bgx+hFizeGJ766LtZrt+9pxTk/OC4zRKLsQpGqPiI7xL noUALyjzwajpWetd3/8GY2xQ5MXB3J6iWEq8rmgwDe+EGcl21vVOCUyFiPrJ4SFaJwOkbR4cx W/5Fwqg3IznN4LV23ENrKm1ANVmzvlfiOzyNecoirEiY41hL58N4ybTgCErXQ5Yw7gpIxrq8V TMJYorCTaM25Vp7F+hihlycDCkqtI74xV0WheV2BKHpOhy2O2EziTCYC9M/DExxcZ35tgtFUQ mLVJjPC8b5mlacx6900tNug2JBTF4gkiaveHiVR0EjYU6AV+c+8El6ed/Jn2O1xSGI0Fu2Cuc LlADnpW6EgeoFMZP3YoRcz6IFTAqd1WUjdKT+0eW9xHoqUnGdDEWDzkdfBvVJqV3bdUhLvp7n 769QEgZAfkz2BskpGFgDc1d5kVqsNaK91os56Fb9iSc7librA+o/KTp8q2mHJJHar65iH19x7 vlPlRnGYdRxPGrUA6/Ssj28jYLy+RiaLf9IL3wxwlPYcdCZM9wYpu6qHtPpfukr/10WqP4tSP V2SZ+sWiDraeW7H1dpx2X5gwZubz3WJKprgcwKswbjdhC8A3X+9yz X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_162249_560255_DDCCC0F5 X-CRM114-Status: GOOD ( 15.06 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Albert Ou , Alexandre Ghiti , Atish Patra , Benjamin Herrenschmidt , Anup Patel , "linux-kernel@vger.kernel.org" , Paul Walmsley , Linux-MM , Paul Mackerras , Zong Li , Michael Ellerman , linux-riscv , linuxppc-dev Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > The eventual goal is to have a split of 3840MB for either user or linear map > > plus and 256MB for vmalloc, including the kernel. Switching between linear > > and user has a noticeable runtime overhead, but it relaxes both the limits > > for user memory and lowmem, and it provides a somewhat stronger > > address space isolation. > > Ya, I think we decided not to do that, at least for now. I guess the right > answer there will depend on what 32-bit systems look like, and since we don't > have any I'm inclined to just stick to the fast option. Makes sense. Actually on 32-bit Arm we see fewer large-memory configurations in new machines than we had in the past before 64-bit machines were widely available at low cost, so I expect not to see a lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips) for cost reasons, and rv32 is likely going to be similar, so you may never really see a need for highmem or the above hack to increase the size of the linear mapping. I just noticed that rv32 allows 2GB of lowmem rather than just the usual 768MB or 1GB, at the expense of addressable user memory. This seems like an unusual choice, but I also don't see any reason to change this or make it more flexible unless actual users appear. Arnd _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 48769C433E0 for ; Wed, 22 Jul 2020 20:22:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 13F2420684 for ; Wed, 22 Jul 2020 20:22:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 13F2420684 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; 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Wed, 22 Jul 2020 20:22:45 +0000 (UTC) X-HE-Tag: toes43_110257626f38 X-Filterd-Recvd-Size: 5027 Received: from mout.kundenserver.de (mout.kundenserver.de [212.227.17.13]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Wed, 22 Jul 2020 20:22:44 +0000 (UTC) Received: from mail-qt1-f179.google.com ([209.85.160.179]) by mrelayeu.kundenserver.de (mreue106 [212.227.15.145]) with ESMTPSA (Nemesis) id 1MWBC8-1kIklV15Ug-00XdiP for ; Wed, 22 Jul 2020 22:22:43 +0200 Received: by mail-qt1-f179.google.com with SMTP id w9so2836869qts.6 for ; Wed, 22 Jul 2020 13:22:42 -0700 (PDT) X-Gm-Message-State: AOAM5332pqyz/TX1S+7kX5HxvNxWeeT6q9ir263S/qAi9JohBlNZmMAm JCf7dxd+MkFm0bEbGtaXxFITtcRlt+wJ11NZoBE= X-Google-Smtp-Source: ABdhPJzomOuvyv87HLrmnRqLMg+xagc+vFRLOHIlCjUhIO6Ps1D+MblDa1Ac6NHH61/GfVpqpoR58oXKvv+qOpTZNZk= X-Received: by 2002:ac8:6743:: with SMTP id n3mr1132159qtp.7.1595449361849; Wed, 22 Jul 2020 13:22:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Arnd Bergmann Date: Wed, 22 Jul 2020 22:22:25 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone To: Palmer Dabbelt Cc: Alexandre Ghiti , Albert Ou , Benjamin Herrenschmidt , Linux-MM , Michael Ellerman , Anup Patel , "linux-kernel@vger.kernel.org" , Atish Patra , Paul Mackerras , Zong Li , Paul Walmsley , linux-riscv , linuxppc-dev Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:m/Clw5vOHf9Gjgkisbe7drGsqPn0Lkmyzo8tstGXzI/gV45y+6K 9U4raGWSYJzrueBxCDmyCS1KZGSdSTtZ6HGyk3RJ+xqUTnBbYLJ12CmuO0rVbiDTyWYcPmo qhv3iRDm4MReCWeglsr+zrk1lbYif/BLqrQxrAAGq53q0xCG4GusMuL1slctqM9yS5lI5F6 UDuUE98gUyKFBtVd/A1Kg== X-UI-Out-Filterresults: notjunk:1;V03:K0:eaaNHJNozp4=:3zh4evzvd1gfmmuZnQHcM7 5qVSHQgPg337XD4bvrYwRBg22n4InNT1rq3cQXM6spaNXJgIhXohE+0ZuMmUIS9iANs1ZBNwR BUZv6QyXlXdLPZIgYbvK6WraYQ/i3hOI3Gu/4oHuhkWJsLKfsa3moq0tm7+Qn3SIRyIBP2cqy WukN5CyQXNFvJkUuCxhF3NglaGCdlt3o8BxTJbj6kjfEgRVekGzt+lXIRPPTS0NF2ATG09CAM RgTtCs0Kw0z0o3Y5VF8jEBDjepKzMHi3aM+JbhrmjCaaj3ZxptytCwrYQVYXnf+kkLc9ishZ7 Gfr3blzbinMB8ijgtgCBxH/XD8b737RAcdpTBEfNkURo1/9phqPsv51hraKqjth3mTgwVaCH2 uvUXuXTGPEQBaQc4MeszoL4Tl08V3Zeecx1z3ho4MG6qVNVSIYhrOuvUwRIa7lzJfyCx8By1u 5CrFKDzF5V6mVvaiAneqSxFIpDyujxrEiz7CkomCGXDTGYEMPYf5rV/u2lVQpSwa/NPXdqPZn agIZmOfV0lglb8padyeTRNsSiL4pdWcLOU0SzgRBt3Ba+uSyg5oIQF8zx1I1S5FzzSLZAE+8A PbInmxKB0AGadovf5I+C/7AR5oqEVi6fIpc3XskIjG2dXmfxatMl8k5/AxiPP1qpofMdAbvI5 6BhPQDf4GQ5MoKMENs34ba1e145M68OK8bIklahQRbvSt+RdMQG/K6tb2vrooP8EiUaxjvHt9 K2qO/ZroXMeuX1yKWSqMjX+DDj04ljoqzAPsigTNKhdfK8q+d3+Qw+Y+BLTgXvKXRqmN+csRF w3axmVv5ejvEc//hQuDUVJWW0XjtU1HB6OU2NjdDn/Yo+w1lzwVFIXJISuV+tPNcdlwV4WJbA 8jxXM2m76PRvDI2jXkaWLdY6Skcuwit8wd9p491fxK1PtFdsEnCoUlJM9Z3jz9LguAvccyPOY s1ebahOHONqzLblVc12bYffFt6Kl4iLbQ1KZISRIVUuHrp5ubCB3h X-Rspamd-Queue-Id: 9886D14391 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > The eventual goal is to have a split of 3840MB for either user or linear map > > plus and 256MB for vmalloc, including the kernel. Switching between linear > > and user has a noticeable runtime overhead, but it relaxes both the limits > > for user memory and lowmem, and it provides a somewhat stronger > > address space isolation. > > Ya, I think we decided not to do that, at least for now. I guess the right > answer there will depend on what 32-bit systems look like, and since we don't > have any I'm inclined to just stick to the fast option. Makes sense. Actually on 32-bit Arm we see fewer large-memory configurations in new machines than we had in the past before 64-bit machines were widely available at low cost, so I expect not to see a lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips) for cost reasons, and rv32 is likely going to be similar, so you may never really see a need for highmem or the above hack to increase the size of the linear mapping. I just noticed that rv32 allows 2GB of lowmem rather than just the usual 768MB or 1GB, at the expense of addressable user memory. This seems like an unusual choice, but I also don't see any reason to change this or make it more flexible unless actual users appear. Arnd 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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 388BCC433E0 for ; Wed, 22 Jul 2020 20:24:35 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 89E4C20684 for ; Wed, 22 Jul 2020 20:24:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 89E4C20684 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BBn4b6ZKXzDqJL for ; Thu, 23 Jul 2020 06:24:31 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=arndb.de (client-ip=212.227.126.133; helo=mout.kundenserver.de; envelope-from=arnd@arndb.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=arndb.de Received: from mout.kundenserver.de (mout.kundenserver.de [212.227.126.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4BBn2d5yhfzDqsb for ; Thu, 23 Jul 2020 06:22:48 +1000 (AEST) Received: from mail-qt1-f176.google.com ([209.85.160.176]) by mrelayeu.kundenserver.de (mreue009 [212.227.15.129]) with ESMTPSA (Nemesis) id 1N6bsM-1ksuzt3hl8-0183zV for ; Wed, 22 Jul 2020 22:22:44 +0200 Received: by mail-qt1-f176.google.com with SMTP id s16so2831941qtn.7 for ; Wed, 22 Jul 2020 13:22:42 -0700 (PDT) X-Gm-Message-State: AOAM530ZlSDw6aiaiROrieCWRGhIWr6QRL2noeW4igTSqSnrisvuKRSp CqFq6vZ9gT0s9O6a7qrxPmL5hIHCgvIHqz7/Dzo= X-Google-Smtp-Source: ABdhPJzomOuvyv87HLrmnRqLMg+xagc+vFRLOHIlCjUhIO6Ps1D+MblDa1Ac6NHH61/GfVpqpoR58oXKvv+qOpTZNZk= X-Received: by 2002:ac8:6743:: with SMTP id n3mr1132159qtp.7.1595449361849; Wed, 22 Jul 2020 13:22:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Arnd Bergmann Date: Wed, 22 Jul 2020 22:22:25 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone To: Palmer Dabbelt Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:igSlMCHB8qHw5Fcfti+sLl7kHvxbFweWd/QG3taVeuXAXJUf+JQ XoZ7a86ZOFYmJubi5TYCcsF2Yjv2+MXzMnZHxc30LEuvQN760T0l11l775YMnAjlfQX69p/ ClWiBvEXoKNC95nwJ8fFLXd3geqSZOSWIvn1O8sCwXcjGNhEQr1tRchyxgvkTVPETpibDtF s2qRgYQSPYWR77fwHdT6A== X-UI-Out-Filterresults: notjunk:1;V03:K0:NI5uOhR3Xjk=:r9rqVHc9+px0ggzsSkg12t LvnqoJgTdYJ6hkdNbAc8xyzY6hpmwSyhYHy12f+Sa4VtjevxWXznoZQsf94CApRsvLnGFO0TZ x/c0WMCeGORs4+eXB+96kOMuxUKC5njAmx1pIsroMCquBZjXqhXUGAajhRRCYkX0XGeDCu1Dy Q+urR/h2JDGp8ZH+n/PO+/dBrYFtA+EFJkZz+/BlhOh3gHqSbAyD+RzMrIQ3FX7ixGD5dvTNT stR2fqwZPC5lV1dgR8ONb5kPcQnbJrhy/9Cq+sprGjGjstOvs+LFyCJt0z+xgmhvtGLdW/w3T oEXfmEmsjGqCf6t1tK1XScx83x3YZnT0rhUNL3QiRLHYXAjdZK8l7up4fiD1J62wvEMordJIK HubxIj8anvKaVfr9MUFAQb7WIpOeIYi4ttc6Iob+DkbYsDOFGe7FY0bqsB0piXjlL6J5dYSva geolKG+R7Gc0OUn1oldUEzQiswTZYRroD+s7Gh2sMyr0rQB4KgCIm70utoV7oM0M2YszQiXX1 ZBmpPaXtlaoBdLWZg0mZw7srocflgaKIhyPdKF+dBb+WHq+hfHJauVdp0sHouvKkgJ76kp6CM yhCApCJTEzH1hqi3axQ1+A9fy5Hup7m6fQug3oibp4DqA+be0zCaDxLFEcN3oIKmDNAuXSE1v 223ABt8qAeJG1F5BowfjQqp7xzMKFURYO/fZT6G3Uy8TrC+gmNUEnAM7EmimmckUA4bDFkdgk 2aTjsug4i2218ifFLGaQU/Y8ttlGGHAroijp7baGGJTLkgpSbq6ATNTlyPM+6C1yholq0ryY9 gbPOLTzqwjEktzI3z0EkgrJXIx/SpkS+YfM2u/ubppPrFKEQWVnIog2g7cF5KNolEfTjSxK X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Albert Ou , Alexandre Ghiti , Atish Patra , Anup Patel , "linux-kernel@vger.kernel.org" , Paul Walmsley , Linux-MM , Paul Mackerras , Zong Li , linux-riscv , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > The eventual goal is to have a split of 3840MB for either user or linear map > > plus and 256MB for vmalloc, including the kernel. Switching between linear > > and user has a noticeable runtime overhead, but it relaxes both the limits > > for user memory and lowmem, and it provides a somewhat stronger > > address space isolation. > > Ya, I think we decided not to do that, at least for now. I guess the right > answer there will depend on what 32-bit systems look like, and since we don't > have any I'm inclined to just stick to the fast option. Makes sense. Actually on 32-bit Arm we see fewer large-memory configurations in new machines than we had in the past before 64-bit machines were widely available at low cost, so I expect not to see a lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips) for cost reasons, and rv32 is likely going to be similar, so you may never really see a need for highmem or the above hack to increase the size of the linear mapping. I just noticed that rv32 allows 2GB of lowmem rather than just the usual 768MB or 1GB, at the expense of addressable user memory. This seems like an unusual choice, but I also don't see any reason to change this or make it more flexible unless actual users appear. Arnd