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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 D023CC433E4 for ; Thu, 23 Jul 2020 22:34:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9CDA6207C4 for ; Thu, 23 Jul 2020 22:34:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9CDA6207C4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3D3018D000A; Thu, 23 Jul 2020 18:34:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3835D8D0003; Thu, 23 Jul 2020 18:34:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 29B228D000A; Thu, 23 Jul 2020 18:34:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0146.hostedemail.com [216.40.44.146]) by kanga.kvack.org (Postfix) with ESMTP id 148158D0003 for ; Thu, 23 Jul 2020 18:34:01 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C1C211802EAD2 for ; Thu, 23 Jul 2020 22:34:00 +0000 (UTC) X-FDA: 77070794640.06.desk13_0907de026f42 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 8C2EF1003DADA for ; Thu, 23 Jul 2020 22:34:00 +0000 (UTC) X-HE-Tag: desk13_0907de026f42 X-Filterd-Recvd-Size: 2505 Received: from kernel.crashing.org (kernel.crashing.org [76.164.61.194]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Thu, 23 Jul 2020 22:33:59 +0000 (UTC) Received: from localhost (gate.crashing.org [63.228.1.57]) (authenticated bits=0) by kernel.crashing.org (8.14.7/8.14.7) with ESMTP id 06NMXDcm005863 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 23 Jul 2020 17:33:16 -0500 Message-ID: <418d5f3d3f42bbc79c5cf30e18ec89edfe2dbd26.camel@kernel.crashing.org> Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone From: Benjamin Herrenschmidt To: Alex Ghiti , Palmer Dabbelt Cc: mpe@ellerman.id.au, paulus@samba.org, Paul Walmsley , aou@eecs.berkeley.edu, Anup Patel , Atish Patra , zong.li@sifive.com, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Date: Fri, 24 Jul 2020 08:33:12 +1000 In-Reply-To: References: <7cb2285e-68ba-6827-5e61-e33a4b65ac03@ghiti.fr> <54af168083aee9dbda1b531227521a26b77ba2c8.camel@kernel.crashing.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8C2EF1003DADA X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Thu, 2020-07-23 at 01:21 -0400, Alex Ghiti wrote: > > works fine with huge pages, what is your problem there ? You rely on > > punching small-page size holes in there ? > > > > ARCH_HAS_STRICT_KERNEL_RWX prevents the use of a hugepage for the kernel > mapping in the direct mapping as it sets different permissions to > different part of the kernel (data, text..etc). Ah ok, that can be solved in a couple of ways... One is to use the linker script to ensure those sections are linked HUGE_PAGE_SIZE appart and moved appropriately by early boot code. One is to selectively degrade just those huge pages. I'm not familiar with the RiscV MMU (I should probably go have a look) but if it's a classic radix tree with huge pages at PUD/PMD level, then you could just degrade the one(s) that cross those boundaries. Cheers, Ben.