From patchwork Wed Aug 9 01:51:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Charlie Jenkins X-Patchwork-Id: 133060 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:c44e:0:b0:3f2:4152:657d with SMTP id w14csp2574865vqr; Tue, 8 Aug 2023 22:20:46 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHbu3Md2Eqi0K1SkVIqsWM9mkaLHnvN1RyRoBDLY4ra7Dh1U6ZDfCuDwAPoezs73th5aXCO X-Received: by 2002:a17:907:2cd8:b0:99c:c4b3:9ff6 with SMTP id hg24-20020a1709072cd800b0099cc4b39ff6mr1082865ejc.48.1691558445749; Tue, 08 Aug 2023 22:20:45 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1691558445; cv=none; d=google.com; s=arc-20160816; b=q/QkyKMFknWe6K+KqEIRrlFFci6eimFKD1Aj9AovoPpos0t5Hu6EDwT68dYNaZ8fdz 1oyPjiaIZfC2KzzzyaPHS+jCtfhLYF2ps4EP1hFls0l17lEFshsAfJGTpUKDtR+Zd63b nZlIvQeHrW2n2LhGJCCoFJD9Uv9ReoSGD5fITGPH1lACvOo5e26JiDTKlfOk5OBRq4uH J3EZfwV0FjOu9f9M26OJTb87y+aaaFVrTSr7P2Kh7V/4Fdf2i7pksM+30uHp//59yD1S VrnIHYJ6aitbVAhth0pQhkBcqw2W3yxDKntSQx7V1cq+f8gbSsM3t5EvlV+AweZ72gPu A7jA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=2tar+fwRF9EwexnZBlGXBQ+bino7OPSUOa9FVKEDgW8=; fh=7AUu9WDHec3ojD+PBWP8kj3GITT/pOnwiCBaYopXpyU=; b=gZWblPdRzjui7jz3qFNuiinYP/dHvngy03fCIn0k4UoC/MXc4t38Bb0SmGizsGKgvX 058W/10RTTMUMg3XwxDJqVNovBz/BealBaKuhhN5DfdzoIyvIw8+cUryc3HxMzJjAbg6 VcwfCeH4L0CI+c9y8XlzTuA4aWFH5sVZ6OAkYjq6hDSdNYW9M2pCXIQV4K4n1tL87jqY G5HdeBSz6wuQZTzuQchGY1SJTsp+2kBchMroxXqPUMklsGRA2sZjXeIcTziJCxoLJXIS NthpBS11+SIJ1WMFOT5KLkqNeufFDtljgR58Im7OuigPkV2+jDMX99P//A3ll1NL7BTJ A1tA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@rivosinc-com.20221208.gappssmtp.com header.s=20221208 header.b=FPpY5cIU; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id v7-20020a170906b00700b00988b6ffa850si8301562ejy.1028.2023.08.08.22.20.13; Tue, 08 Aug 2023 22:20:45 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@rivosinc-com.20221208.gappssmtp.com header.s=20221208 header.b=FPpY5cIU; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231344AbjHIBxU (ORCPT + 99 others); Tue, 8 Aug 2023 21:53:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231273AbjHIBxP (ORCPT ); Tue, 8 Aug 2023 21:53:15 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CD411BEF for ; Tue, 8 Aug 2023 18:53:13 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id d9443c01a7336-1bc6bfc4b58so18366545ad.1 for ; Tue, 08 Aug 2023 18:53:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20221208.gappssmtp.com; s=20221208; t=1691545992; x=1692150792; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=2tar+fwRF9EwexnZBlGXBQ+bino7OPSUOa9FVKEDgW8=; b=FPpY5cIUXnip2ZGbpSphNOYtcmoz+9UqNCzoKTIuGrXSltzFcKRrlt8IZVpkHLRqCx OnkTugPfEWDKKQRJ75G2J1aJXt6PH8fts5QVkJJs8njOPLx6pNBBDKHzo/kPhqxS0sx3 1HU8/tEpAVmLFR+F4zwPNJwDwa/GS5jdzeVtMhkd3NlduxYlQA9dfzjF/ys4sjj6OEtk sjDMhjLy6jjBKzFs07exQfX4lKo012NsKC4Zu68gj0Uv/D7Nb/c/EwcN8oQMkTg6va+w mYmQCyjU8OGyh+PyGz8lSNWVUIf8yU596h/YkYk7J+SNhMSNxobFIMZoGtxQE5T5cv3X /BDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691545992; x=1692150792; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=2tar+fwRF9EwexnZBlGXBQ+bino7OPSUOa9FVKEDgW8=; b=UdpetQtHVAVvv0bpQCcdSbS+VgZ34Cz5dxMoWdUwdMxVImI4EtrNAKrxr2EmBMsP8n 9L4rCVuYL6YwikAHi8ar1LE0lI1SBVAaFA4jyExPooNJ8H8/1aZI9HqQEceyy123LorG Ci22xSsNeF6gI1cDMniR0YFzQfjrL7FoECQ6LlNEgwDSOyaBau3zxXorhYk8yCc3HOtb MmUa3J7uLfmjAcLGGsK5C8+eotlMvw+Dhmo25+KhbdgZWq60eG5kQtwoH9UOnzYtP2lS uh3iMHgRqDBHIb1O/8LfOOpMNfuKy72Bvv1x6xY8B/Se1yDeOk6VQxcklKZTSJNEzyfk 3tBA== X-Gm-Message-State: AOJu0YxvXCeV2cw93MKsW5ceI8FYY175Fqy+2atQSw9VDXENk71YnNSa jGFd55e3E0GIAuAS8LomwA28yw== X-Received: by 2002:a17:903:1207:b0:1b8:6850:c3c4 with SMTP id l7-20020a170903120700b001b86850c3c4mr1594061plh.22.1691545992539; Tue, 08 Aug 2023 18:53:12 -0700 (PDT) Received: from charlie.ba.rivosinc.com ([66.220.2.162]) by smtp.gmail.com with ESMTPSA id bj7-20020a170902850700b001b87bedcc6fsm9657591plb.93.2023.08.08.18.53.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Aug 2023 18:53:12 -0700 (PDT) From: Charlie Jenkins To: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: charlie@rivosinc.com, conor@kernel.org, paul.walmsley@sifive.com, palmer@rivosinc.com, aou@eecs.berkeley.edu, anup@brainfault.org, konstantin@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mick@ics.forth.gr, jrtc27@jrtc27.com, rdunlap@infradead.org, alexghiti@rivosinc.com Subject: [PATCH v9 4/4] RISC-V: mm: Document mmap changes Date: Tue, 8 Aug 2023 18:51:10 -0700 Message-Id: <20230809015110.3290774-5-charlie@rivosinc.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230809015110.3290774-1-charlie@rivosinc.com> References: <20230809015110.3290774-1-charlie@rivosinc.com> MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1773727589050416966 X-GMAIL-MSGID: 1773727589050416966 The behavior of mmap is modified with this patch series, so explain the changes to the mmap hint address behavior. Signed-off-by: Charlie Jenkins Reviewed-by: Alexandre Ghiti --- Documentation/riscv/vm-layout.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst index 5462c84f4723..69ff6da1dbf8 100644 --- a/Documentation/riscv/vm-layout.rst +++ b/Documentation/riscv/vm-layout.rst @@ -133,3 +133,25 @@ RISC-V Linux Kernel SV57 ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel __________________|____________|__________________|_________|____________________________________________________________ + + +Userspace VAs +-------------------- +To maintain compatibility with software that relies on the VA space with a +maximum of 48 bits the kernel will, by default, return virtual addresses to +userspace from a 48-bit range (sv48). This default behavior is achieved by +passing 0 into the hint address parameter of mmap. On CPUs with an address space +smaller than sv48, the CPU maximum supported address space will be the default. + +Software can "opt-in" to receiving VAs from another VA space by providing +a hint address to mmap. A hint address passed to mmap will cause the largest +address space that fits entirely into the hint to be used, unless there is no +space left in the address space. If there is no space available in the requested +address space, an address in the next smallest available address space will be +returned. + +For example, in order to obtain 48-bit VA space, a hint address greater than +:code:`1 << 47` must be provided. Note that this is 47 due to sv48 userspace +ending at :code:`1 << 47` and the addresses beyond this are reserved for the +kernel. Similarly, to obtain 57-bit VA space addresses, a hint address greater +than or equal to :code:`1 << 56` must be provided.