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path: root/arch/riscv/include/asm/csr.h
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2021-04-26riscv: Introduce alternative mechanism to apply errata solutionVincent Chen1-0/+3
Introduce the "alternative" mechanism from ARM64 and x86 to apply the CPU vendors' errata solution at runtime. The main purpose of this patch is to provide a framework. Therefore, the implementation is quite basic for now so that some scenarios could not use this schemei, such as patching code to a module, relocating the patching code and heterogeneous CPU topology. Users could use the macro ALTERNATIVE to apply an errata to the existing code flow. In the macro ALTERNATIVE, users need to specify the manufacturer information(vendorid, archid, and impid) for this errata. Therefore, kernel will know this errata is suitable for which CPU core. During the booting procedure, kernel will select the errata required by the CPU core and then patch it. It means that the kernel only applies the errata to the specified CPU core. In this case, the vendor's errata does not affect each other at runtime. The above patching procedure only occurs during the booting phase, so we only take the overhead of the "alternative" mechanism once. This "alternative" mechanism is enabled by default to ensure that all required errata will be applied. However, users can disable this feature by the Kconfig "CONFIG_RISCV_ERRATA_ALTERNATIVE". Signed-off-by: Vincent Chen <vincent.chen@sifive.com> Reviewed-by: Anup Patel <anup@brainfault.org> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2021-02-19RISC-V: Implement ASID allocatorAnup Patel1-0/+6
Currently, we do local TLB flush on every MM switch. This is very harsh on performance because we are forcing page table walks after every MM switch. This patch implements ASID allocator for assigning an ASID to a MM context. The number of ASIDs are limited in HW so we create a logical entity named CONTEXTID for assigning to MM context. The lower bits of CONTEXTID are ASID and upper bits are VERSION number. The number of usable ASID bits supported by HW are detected at boot-time by writing 1s to ASID bits in SATP CSR. We allocate new CONTEXTID on first MM switch for a MM context where the ASID is allocated from an ASID bitmap and VERSION is provide by an atomic counter. At time of allocating new CONTEXTID, if we run out of available ASIDs then: 1. We flush the ASID bitmap 2. Increment current VERSION atomic counter 3. Re-allocate ASID from ASID bitmap 4. Flush TLB on all CPUs 5. Try CONTEXTID re-assignment on all CPUs Please note that we don't use ASID #0 because it is used at boot-time by all CPUs for initial MM context. Also, newly created context is always assigned CONTEXTID #0 (i.e. VERSION #0 and ASID #0) which is an invalid context in our implementation. Using above approach, we have virtually infinite CONTEXTIDs on-top-of limited number of HW ASIDs. This approach is inspired from ASID allocator used for Linux ARM/ARM64 but we have adapted it for RISC-V. Overall, this ASID allocator helps us reduce rate of local TLB flushes on every CPU thereby increasing performance. This patch is tested on QEMU virt machine, Spike and SiFive Unleashed board. On QEMU virt machine, we see some (3-5% approx) performance improvement with SW emulated TLBs provided by QEMU. Unfortunately, the ASID bits of the SATP CSR are not implemented on Spike and SiFive Unleashed board so we don't see any change in performance. On real HW having all ASID bits implemented, the performance gains will be much more due improved sharing of TLB among different processes. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2020-05-05RISC-V: Remove N-extension related definesAnup Patel1-3/+0
The RISC-V N-extension is still in draft state hence remove N-extension related defines from asm/csr.h. Signed-off-by: Anup Patel <anup.patel@wdc.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2020-02-18riscv: set pmp configuration if kernel is running in M-modeGreentime Hu1-0/+12
When the kernel is running in S-mode, the expectation is that the bootloader or SBI layer will configure the PMP to allow the kernel to access physical memory. But, when the kernel is running in M-mode and is started with the ELF "loader", there's probably no bootloader or SBI layer involved to configure the PMP. Thus, we need to configure the PMP ourselves to enable the kernel to access all regions. Signed-off-by: Greentime Hu <greentime.hu@sifive.com> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2020-01-05riscv: prefix IRQ_ macro names with an RV_ namespacePaul Walmsley1-9/+9
"IRQ_TIMER", used in the arch/riscv CSR header file, is a sufficiently generic macro name that it's used by several source files across the Linux code base. Some of these other files ultimately include the arch/riscv CSR include file, causing collisions. Fix by prefixing the RISC-V csr.h IRQ_ macro names with an RV_ prefix. Fixes: a4c3733d32a72 ("riscv: abstract out CSR names for supervisor vs machine mode") Reported-by: Olof Johansson <olof@lixom.net> Acked-by: Olof Johansson <olof@lixom.net> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
2019-11-18riscv: clear the instruction cache and all registers when bootingChristoph Hellwig1-0/+1
When we get booted we want a clear slate without any leaks from previous supervisors or the firmware. Flush the instruction cache and then clear all registers to known good values. This is really important for the upcoming nommu support that runs on M-mode, but can't really harm when running in S-mode either. Vaguely based on the concepts from opensbi. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Anup Patel <anup@brainfault.org> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
2019-11-18riscv: read the hart ID from mhartid on bootDamien Le Moal1-0/+1
When in M-Mode, we can use the mhartid CSR to get the ID of the running HART. Doing so, direct M-Mode boot without firmware is possible. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Anup Patel <anup@brainfault.org> Reviewed-by: Atish Patra <atish.patra@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
2019-11-05riscv: abstract out CSR names for supervisor vs machine modeChristoph Hellwig1-10/+62
Many of the privileged CSRs exist in a supervisor and machine version that are used very similarly. Provide versions of the CSR names and fields that map to either the S-mode or M-mode variant depending on a new CONFIG_RISCV_M_MODE kconfig symbol. Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com> and Paul Walmsley <paul.walmsley@sifive.com>. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> # for drivers/clocksource, drivers/irqchip [paul.walmsley@sifive.com: updated to apply] Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
2019-06-05treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 286Thomas Gleixner1-9/+1
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation version 2 this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 97 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190529141901.025053186@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-17RISC-V: Access CSRs using CSR numbersAnup Patel1-7/+25
We should prefer accessing CSRs using their CSR numbers because: 1. It compiles fine with older toolchains. 2. We can use latest CSR names in #define macro names of CSR numbers as-per RISC-V spec. 3. We can access newly added CSRs even if toolchain does not recognize newly addes CSRs by name. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2019-05-17RISC-V: Add interrupt related SCAUSE defines in asm/csr.hAnup Patel1-4/+17
This patch adds SCAUSE interrupt flag and SCAUSE interrupt related defines to asm/csr.h. We also use these defines in kernel/irq.c and express SIE/SIP flags in-terms of SCAUSE interrupt causes. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2019-05-17RISC-V: Use tabs to align macro values in asm/csr.hAnup Patel1-38/+38
The spacing between macro name and value is not consistent in asm/csr.h. This patch beautifies asm/csr.h by using tabs to align macro values instead of spaces. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2018-08-13RISC-V: add a definition for the SIE SEIE bitChristoph Hellwig1-0/+1
This mirrors the SIE_SSIE and SETE bits that are used in a similar fashion. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2018-01-31riscv: rename sptbr to satpChristoph Hellwig1-7/+7
satp is the name used by the current privileged spec 1.10, use it instead of the old name. The most recent release binutils release (2.29) doesn't know about the satp name yet, so stick to the name from the previous privileged ISA release and comment on the fact. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2018-01-08riscv: rename SR_* constants to match the specChristoph Hellwig1-4/+4
Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
2017-09-27RISC-V: Generic library routines and assemblyPalmer Dabbelt1-0/+132
This patch contains code that is more specific to the RISC-V ISA than it is to Linux. It contains string and math operations, C wrappers for various assembly instructions, stack walking code, and uaccess. Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
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