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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id z10-20020a7bc7ca000000b003f8f8fc3c32sm7934552wmk.31.2023.06.26.07.36.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jun 2023 07:36:28 -0700 (PDT) From: Alexandre Ghiti To: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Andrew Jones , Conor Dooley , Sunil V L , Song Shuai , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Alexandre Ghiti , Atish Patra Subject: [PATCH v4 1/3] Documentation: arm: Add bootargs to the table of added DT parameters Date: Mon, 26 Jun 2023 16:36:24 +0200 Message-Id: <20230626143626.106584-1-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE 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: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1769777285707590759?= X-GMAIL-MSGID: =?utf-8?q?1769777285707590759?= The bootargs node is also added by the EFI stub in the function update_fdt(), so add it to the table. Signed-off-by: Alexandre Ghiti Reviewed-by: Atish Patra Reviewed-by: Song Shuai --- Documentation/arm/uefi.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/arm/uefi.rst b/Documentation/arm/uefi.rst index baebe688a006..2b7ad9bd7cd2 100644 --- a/Documentation/arm/uefi.rst +++ b/Documentation/arm/uefi.rst @@ -50,7 +50,7 @@ The stub populates the FDT /chosen node with (and the kernel scans for) the following parameters: ========================== ====== =========================================== -Name Size Description +Name Type Description ========================== ====== =========================================== linux,uefi-system-table 64-bit Physical address of the UEFI System Table. @@ -67,4 +67,6 @@ linux,uefi-mmap-desc-ver 32-bit Version of the mmap descriptor format. kaslr-seed 64-bit Entropy used to randomize the kernel image base address location. + +bootargs String Kernel command line ========================== ====== =========================================== From patchwork Mon Jun 26 14:36:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 112995 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:994d:0:b0:3d9:f83d:47d9 with SMTP id k13csp7543781vqr; Mon, 26 Jun 2023 08:00:48 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6OyRaxhlBkN49/JQun/YxQ1U+UV38nywjjkMrYMbDXdHRAg2y9+TzfvBFf4oJciJToBB1t X-Received: by 2002:a17:902:f551:b0:1b8:69f:f169 with SMTP id h17-20020a170902f55100b001b8069ff169mr2521220plf.30.1687791647639; Mon, 26 Jun 2023 08:00:47 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1687791647; cv=none; d=google.com; s=arc-20160816; b=nRSQlF++5GrTkppgT6w2GcZFw3IrN/YyNokZV1fFVYoeE7r9rUD4eYj4z3oerpCmto ppfNT1dvzzHfqWNyIxjBZcakIu691KaBZtmmfmaULg8pmCW7FCIEQkwWlLv7PkPThd8u ZYepridVV7g0+ZEZAdKuaEDRDM9sVVCeP35s2b/q82AAAQiHPiB+zLQYqqzeMTW8cZNj Faj1wQkTBIBl9S4j6M+bpCScqqEAMGQkzI5aDpUDXoEgPfq3yugBBCTmvwb3rr+Ih9s9 n7VC0BPdjE6T6AbNMKH8ANRxFQxwjFTynKwk61laCteAXv3xY5w8B8b257VSLHKsDxy6 25lA== 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=APwyby8MHvPbj/+Q6ciqlRQJlAXkF02ht9f+NF2/vFw=; fh=q1TyRXd/fof/fvrVte+wAvuKBr85cFVMQ9E2Fd/PvME=; b=H8DD1+xjFTqiHM8K/Hh5RnNvi8CLmM5JOe7A9VCQYOX/IgKhX+JGnp7O1vwMBQVfzX 6tyLM0YMxLadiRMLMZhvMZTgGHZ3kiPZMsvd/AMSpIzMBDgB36qKxrOSzFZ17Wzq+H4N MbSxhUzro8hXecD+jGlyDDetS1kEb8pBa1nDGubSGqgh7eLC/zHVhJJtQDOiRJ7GM45i MvC0pI/Uurmma8FuXSQY/iQRnZ306yYTs+a+iFA9ACJIOATGsAN/hwgIjLJzuC1n7/EM nV0zCVfQmuDgFOHBkYM2IsACKwUyhmoFrgVZK0l0P9KIc5PcV4fhOMKKLzv9CZ9jawR9 ZMAg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@rivosinc-com.20221208.gappssmtp.com header.s=20221208 header.b=Ir2iuPX8; 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. 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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id a25-20020a5d4579000000b003048477729asm7566182wrc.81.2023.06.26.07.37.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jun 2023 07:37:29 -0700 (PDT) From: Alexandre Ghiti To: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Andrew Jones , Conor Dooley , Sunil V L , Song Shuai , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Alexandre Ghiti , Palmer Dabbelt , Atish Patra Subject: [PATCH v4 2/3] Documentation: riscv: Add early boot document Date: Mon, 26 Jun 2023 16:36:25 +0200 Message-Id: <20230626143626.106584-2-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230626143626.106584-1-alexghiti@rivosinc.com> References: <20230626143626.106584-1-alexghiti@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_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE 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: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1769777814593161849?= X-GMAIL-MSGID: =?utf-8?q?1769777814593161849?= This document describes the constraints and requirements of the early boot process in a RISC-V kernel. Signed-off-by: Alexandre Ghiti Reviewed-by: Björn Töpel Reviewed-by: Conor Dooley Reviewed-by: Sunil V L Reviewed-by: Andrew Jones Reviewed-by: Palmer Dabbelt Reviewed-by: Atish Patra Reviewed-by: Song Shuai Acked-by: Palmer Dabbelt Acked-by: Palmer Dabbelt --- Documentation/riscv/boot-image-header.rst | 3 - Documentation/riscv/boot.rst | 169 ++++++++++++++++++++++ Documentation/riscv/index.rst | 1 + 3 files changed, 170 insertions(+), 3 deletions(-) create mode 100644 Documentation/riscv/boot.rst diff --git a/Documentation/riscv/boot-image-header.rst b/Documentation/riscv/boot-image-header.rst index d7752533865f..a4a45310c4c4 100644 --- a/Documentation/riscv/boot-image-header.rst +++ b/Documentation/riscv/boot-image-header.rst @@ -7,9 +7,6 @@ Boot image header in RISC-V Linux This document only describes the boot image header details for RISC-V Linux. -TODO: - Write a complete booting guide. - The following 64-byte header is present in decompressed Linux kernel image:: u32 code0; /* Executable code */ diff --git a/Documentation/riscv/boot.rst b/Documentation/riscv/boot.rst new file mode 100644 index 000000000000..f890ac442c91 --- /dev/null +++ b/Documentation/riscv/boot.rst @@ -0,0 +1,169 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================================== +RISC-V Kernel Boot Requirements and Constraints +=============================================== + +:Author: Alexandre Ghiti +:Date: 23 May 2023 + +This document describes what the RISC-V kernel expects from bootloaders and +firmware, but also the constraints that any developer must have in mind when +touching the early boot process. For the purposes of this document, the +``early boot process`` refers to any code that runs before the final virtual +mapping is set up. + +Pre-kernel Requirements and Constraints +======================================= + +The RISC-V kernel expects the following of bootloaders and platform firmware: + +Register state +-------------- + +The RISC-V kernel expects: + + * ``$a0`` to contain the hartid of the current core. + * ``$a1`` to contain the address of the devicetree in memory. + +CSR state +--------- + +The RISC-V kernel expects: + + * ``$satp = 0``: the MMU, if present, must be disabled. + +Reserved memory for resident firmware +------------------------------------- + +The RISC-V kernel must not map any resident memory, or memory protected with +PMPs, in the direct mapping, so the firmware must correctly mark those regions +as per the devicetree specification and/or the UEFI specification. + +Kernel location +--------------- + +The RISC-V kernel expects to be placed at a PMD boundary (2MB aligned for rv64 +and 4MB aligned for rv32). Note that the EFI stub will physically relocate the +kernel if that's not the case. + +Hardware description +-------------------- + +The firmware can pass either a devicetree or ACPI tables to the RISC-V kernel. + +The devicetree is either passed directly to the kernel from the previous stage +using the ``$a1`` register, or when booting with UEFI, it can be passed using the +EFI configuration table. + +The ACPI tables are passed to the kernel using the EFI configuration table. In +this case, a tiny devicetree is still created by the EFI stub. Please refer to +"EFI stub and devicetree" section below for details about this devicetree. + +Kernel entrance +--------------- + +On SMP systems, there are 2 methods to enter the kernel: + +- ``RISCV_BOOT_SPINWAIT``: the firmware releases all harts in the kernel, one hart + wins a lottery and executes the early boot code while the other harts are + parked waiting for the initialization to finish. This method is mostly used to + support older firmwares without SBI HSM extension and M-mode RISC-V kernel. +- ``Ordered booting``: the firmware releases only one hart that will execute the + initialization phase and then will start all other harts using the SBI HSM + extension. The ordered booting method is the preferred booting method for + booting the RISC-V kernel because it can support cpu hotplug and kexec. + +UEFI +---- + +UEFI memory map +~~~~~~~~~~~~~~~ + +When booting with UEFI, the RISC-V kernel will use only the EFI memory map to +populate the system memory. + +The UEFI firmware must parse the subnodes of the ``/reserved-memory`` devicetree +node and abide by the devicetree specification to convert the attributes of +those subnodes (``no-map`` and ``reusable``) into their correct EFI equivalent +(refer to section "3.5.4 /reserved-memory and UEFI" of the devicetree +specification v0.4-rc1). + +RISCV_EFI_BOOT_PROTOCOL +~~~~~~~~~~~~~~~~~~~~~~~ + +When booting with UEFI, the EFI stub requires the boot hartid in order to pass +it to the RISC-V kernel in ``$a1``. The EFI stub retrieves the boot hartid using +one of the following methods: + +- ``RISCV_EFI_BOOT_PROTOCOL`` (**preferred**). +- ``boot-hartid`` devicetree subnode (**deprecated**). + +Any new firmware must implement ``RISCV_EFI_BOOT_PROTOCOL`` as the devicetree +based approach is deprecated now. + +Early Boot Requirements and Constraints +======================================= + +The RISC-V kernel's early boot process operates under the following constraints: + +EFI stub and devicetree +----------------------- + +When booting with UEFI, the devicetree is supplemented (or created) by the EFI +stub with the same parameters as arm64 which are described at the paragraph +"UEFI kernel support on ARM" in Documentation/arm/uefi.rst. + +Virtual mapping installation +---------------------------- + +The installation of the virtual mapping is done in 2 steps in the RISC-V kernel: + +1. ``setup_vm()`` installs a temporary kernel mapping in ``early_pg_dir`` which + allows discovery of the system memory. Only the kernel text/data are mapped + at this point. When establishing this mapping, no allocation can be done + (since the system memory is not known yet), so ``early_pg_dir`` page table is + statically allocated (using only one table for each level). + +2. ``setup_vm_final()`` creates the final kernel mapping in ``swapper_pg_dir`` + and takes advantage of the discovered system memory to create the linear + mapping. When establishing this mapping, the kernel can allocate memory but + cannot access it directly (since the direct mapping is not present yet), so + it uses temporary mappings in the fixmap region to be able to access the + newly allocated page table levels. + +For ``virt_to_phys()`` and ``phys_to_virt()`` to be able to correctly convert +direct mapping addresses to physical addresses, they need to know the start of +the DRAM. This happens after step 1, right before step 2 installs the direct +mapping (see ``setup_bootmem()`` function in arch/riscv/mm/init.c). Any usage of +those macros before the final virtual mapping is installed must be carefully +examined. + +Devicetree mapping via fixmap +----------------------------- + +As the ``reserved_mem`` array is initialized with virtual addresses established +by ``setup_vm()``, and used with the mapping established by +``setup_vm_final()``, the RISC-V kernel uses the fixmap region to map the +devicetree. This ensures that the devicetree remains accessible by both virtual +mappings. + +Pre-MMU execution +----------------- + +A few pieces of code need to run before even the first virtual mapping is +established. These are the installation of the first virtual mapping itself, +patching of early alternatives and the early parsing of the kernel command line. +That code must be very carefully compiled as: + +- ``-fno-pie``: This is needed for relocatable kernels which use ``-fPIE``, + since otherwise, any access to a global symbol would go through the GOT which + is only relocated virtually. +- ``-mcmodel=medany``: Any access to a global symbol must be PC-relative to + avoid any relocations to happen before the MMU is setup. +- *all* instrumentation must also be disabled (that includes KASAN, ftrace and + others). + +As using a symbol from a different compilation unit requires this unit to be +compiled with those flags, we advise, as much as possible, not to use external +symbols. diff --git a/Documentation/riscv/index.rst b/Documentation/riscv/index.rst index 175a91db0200..1f66062def6d 100644 --- a/Documentation/riscv/index.rst +++ b/Documentation/riscv/index.rst @@ -5,6 +5,7 @@ RISC-V architecture .. toctree:: :maxdepth: 1 + boot boot-image-header vm-layout hwprobe From patchwork Mon Jun 26 14:36:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 112997 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:994d:0:b0:3d9:f83d:47d9 with SMTP id k13csp7548550vqr; Mon, 26 Jun 2023 08:05:44 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6BP1hIQH5DavMiAfk/iu7Wz43wo0EpdcklpD9CLAYM5W6WjAJFpNc3GEq2Qyd/xXtoV7nK X-Received: by 2002:a17:907:980e:b0:98c:e0b5:f0cc with SMTP id ji14-20020a170907980e00b0098ce0b5f0ccmr11137939ejc.75.1687791943842; Mon, 26 Jun 2023 08:05:43 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1687791943; cv=none; d=google.com; s=arc-20160816; b=LzyWxS3XoX4qbHsZXla5rwsuoy5G6pUy8vTkYGFdsHelmkV8+a8Y48v2pB6MTV4asD 2cWwxgTpfq2y7jCwY5C793EZQDRjC5lRSUN6LYwzLNkzIPCjg/VVlrxS4fshZRc0dn41 xocjEmTCeY24pu7W2qP7Bu8hObnx2k6/21ZCl/IsUe1GZspCsEHbaxA/TKhfPsNBjVHU Q4hjMZ1YF2GuPBcG9eSbAPmHP76wB+gj0ZJFHMPVrpuL5+ZamtRpv7wgIpzamui35KYn lZ5tPLJe6kTiutE6ULkIDGOCy2Lmc0hF4OErpMyS1jKSjq+2NjXxm45exa/rwAhZ7qxa j+RQ== 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=/pQzPxsmpV8ILmUDokZDt4x2j1OZGQdakvLzX04+Ejg=; fh=EcOnDBL5c3S2nEiYhWSY4B8a1rCPHIQEJ35Tu95NEHc=; b=ff7E01T5L2Rcu79YXHADrpN1mGahrqzZYek7UrOtPoeBhTPPWa7Tl4/HmW9mYvDV5z UNG+HiEaoePNsp6wi5QeS+DpdGXfkbmz3uMl1F2FCfuCc7Y7Eoy8Ktk5/oSBOxcutwOK 95sZhYOhmaouW6312pYYudsw4Eg/zJHea9hx+GOITjrX0whL0Hi+X5V5rOv2YrAF6qmZ WMzFHF3VkfqCtq87hyKYgatSrPf1iAeYCoqcfIpihsp54+HzlcPiwJN01GONkCGfDO1B ej/oPrPQBbdT4m6pPcmJZkbLId3/rWjqJLGB4hlxIyD8/FAwDUDhJJobPlRSlR4zRNAF HPgg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@rivosinc-com.20221208.gappssmtp.com header.s=20221208 header.b=uex3RA9q; 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. 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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id v2-20020a5d6782000000b00313f5babb18sm1644944wru.9.2023.06.26.07.38.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jun 2023 07:38:30 -0700 (PDT) From: Alexandre Ghiti To: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Andrew Jones , Conor Dooley , Sunil V L , Song Shuai , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Alexandre Ghiti , Atish Patra , Palmer Dabbelt Subject: [PATCH v4 3/3] Documentation: riscv: Update boot image header since EFI stub is supported Date: Mon, 26 Jun 2023 16:36:26 +0200 Message-Id: <20230626143626.106584-3-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230626143626.106584-1-alexghiti@rivosinc.com> References: <20230626143626.106584-1-alexghiti@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_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE 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: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1769778125595774270?= X-GMAIL-MSGID: =?utf-8?q?1769778125595774270?= The EFI stub is supported on RISC-V so update the documentation that explains how the boot image header was reused to support it. Signed-off-by: Alexandre Ghiti Reviewed-by: Atish Patra Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Acked-by: Palmer Dabbelt --- Documentation/riscv/boot-image-header.rst | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/Documentation/riscv/boot-image-header.rst b/Documentation/riscv/boot-image-header.rst index a4a45310c4c4..df2ffc173e80 100644 --- a/Documentation/riscv/boot-image-header.rst +++ b/Documentation/riscv/boot-image-header.rst @@ -28,11 +28,11 @@ header in future. Notes ===== -- This header can also be reused to support EFI stub for RISC-V in future. EFI - specification needs PE/COFF image header in the beginning of the kernel image - in order to load it as an EFI application. In order to support EFI stub, - code0 should be replaced with "MZ" magic string and res3(at offset 0x3c) should - point to the rest of the PE/COFF header. +- This header is also reused to support EFI stub for RISC-V. EFI specification + needs PE/COFF image header in the beginning of the kernel image in order to + load it as an EFI application. In order to support EFI stub, code0 is replaced + with "MZ" magic string and res3(at offset 0x3c) points to the rest of the + PE/COFF header. - version field indicate header version number