From patchwork Thu Feb 25 08:04:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 12103611 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 4C603C433DB for ; Thu, 25 Feb 2021 08:07:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 97AEA64EF1 for ; Thu, 25 Feb 2021 08:07:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97AEA64EF1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ghiti.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 123358D0009; Thu, 25 Feb 2021 03:07:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0D3F98D0005; Thu, 25 Feb 2021 03:07:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F05318D0009; Thu, 25 Feb 2021 03:07:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0154.hostedemail.com [216.40.44.154]) by kanga.kvack.org (Postfix) with ESMTP id D97E98D0005 for ; Thu, 25 Feb 2021 03:07:36 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A83C3EFDF for ; Thu, 25 Feb 2021 08:07:36 +0000 (UTC) X-FDA: 77856060912.03.ABF6883 Received: from relay5-d.mail.gandi.net (relay5-d.mail.gandi.net [217.70.183.197]) by imf18.hostedemail.com (Postfix) with ESMTP id 3EE8B2000395 for ; Thu, 25 Feb 2021 08:07:37 +0000 (UTC) X-Originating-IP: 81.185.161.35 Received: from localhost.localdomain (35.161.185.81.rev.sfr.net [81.185.161.35]) (Authenticated sender: alex@ghiti.fr) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id 8DAD41C0006; Thu, 25 Feb 2021 08:07:26 +0000 (UTC) From: Alexandre Ghiti To: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Arnd Bergmann , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-arch@vger.kernel.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH 2/3] Documentation: riscv: Add documentation that describes the VM layout Date: Thu, 25 Feb 2021 03:04:52 -0500 Message-Id: <20210225080453.1314-3-alex@ghiti.fr> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210225080453.1314-1-alex@ghiti.fr> References: <20210225080453.1314-1-alex@ghiti.fr> MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3EE8B2000395 X-Stat-Signature: g57f1nmo3eicx1c99zaschukirby3wqs Received-SPF: none (ghiti.fr>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=relay5-d.mail.gandi.net; client-ip=217.70.183.197 X-HE-DKIM-Result: none/none X-HE-Tag: 1614240457-794273 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: This new document presents the RISC-V virtual memory layout and is based one the x86 one: it describes the different limits of the different regions of the virtual address space. Signed-off-by: Alexandre Ghiti --- Documentation/riscv/index.rst | 1 + Documentation/riscv/vm-layout.rst | 61 +++++++++++++++++++++++++++++++ 2 files changed, 62 insertions(+) create mode 100644 Documentation/riscv/vm-layout.rst diff --git a/Documentation/riscv/index.rst b/Documentation/riscv/index.rst index 6e6e39482502..ea915c196048 100644 --- a/Documentation/riscv/index.rst +++ b/Documentation/riscv/index.rst @@ -6,6 +6,7 @@ RISC-V architecture :maxdepth: 1 boot-image-header + vm-layout pmu patch-acceptance diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst new file mode 100644 index 000000000000..e8e569e2686a --- /dev/null +++ b/Documentation/riscv/vm-layout.rst @@ -0,0 +1,61 @@ +===================================== +Virtual Memory Layout on RISC-V Linux +===================================== + +:Author: Alexandre Ghiti +:Date: 12 February 2021 + +This document describes the virtual memory layout used by the RISC-V Linux +Kernel. + +RISC-V Linux Kernel 32bit +========================= + +RISC-V Linux Kernel SV32 +------------------------ + +TODO + +RISC-V Linux Kernel 64bit +========================= + +The RISC-V privileged architecture document states that the 64bit addresses +"must have bits 63–48 all equal to bit 47, or else a page-fault exception will +occur.": that splits the virtual address space into 2 halves separated by a very +big hole, the lower half is where the userspace resides, the upper half is where +the RISC-V Linux Kernel resides. + +RISC-V Linux Kernel SV39 +------------------------ + +:: + + ======================================================================================================================== + Start addr | Offset | End addr | Size | VM area description + ======================================================================================================================== + | | | | + 0000000000000000 | 0 | 0000003fffffffff | 256 GB | user-space virtual memory, different per mm + __________________|____________|__________________|_________|___________________________________________________________ + | | | | + 0000004000000000 | +256 GB | ffffffbfffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical + | | | | virtual memory addresses up to the -256 GB + | | | | starting offset of kernel mappings. + __________________|____________|__________________|_________|___________________________________________________________ + | + | Kernel-space virtual memory, shared between all processes: + ____________________________________________________________|___________________________________________________________ + | | | | + ffffffc000000000 | -256 GB | ffffffc7ffffffff | 32 GB | kasan + ffffffcefee00000 | -196 GB | ffffffcefeffffff | 2 MB | fixmap + ffffffceff000000 | -196 GB | ffffffceffffffff | 16 MB | PCI io + ffffffcf00000000 | -196 GB | ffffffcfffffffff | 4 GB | vmemmap + ffffffd000000000 | -192 GB | ffffffdfffffffff | 64 GB | vmalloc/ioremap space + ffffffe000000000 | -128 GB | ffffffff7fffffff | 126 GB | direct mapping of all physical memory + __________________|____________|__________________|_________|____________________________________________________________ + | + | + ____________________________________________________________|____________________________________________________________ + | | | | + ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules + ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel, BPF + __________________|____________|__________________|_________|____________________________________________________________