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commit914d6f44fc("RISC-V: only iterate over possible CPUs in ISA string parser") changed riscv_fill_hwcap() from iterating over CPU DT nodes to iterating over logical CPU IDs. Since this function runs long before cpu_dev_init() creates CPU devices, it hits the fallback path in of_cpu_device_node_get(), which itself iterates over the DT nodes, searching for a node with the requested CPU ID. (Incidentally, this makes riscv_fill_hwcap() now take quadratic time.) riscv_fill_hwcap() passes a logical CPU ID to of_cpu_device_node_get(), which uses the arch_match_cpu_phys_id() hook to translate the logical ID to a physical ID as found in the DT. arch_match_cpu_phys_id() has a generic weak definition, and RISC-V provides a strong definition using cpuid_to_hartid_map(). However, the RISC-V specific implementation is located in arch/riscv/kernel/smp.c, and that file is only compiled when SMP is enabled. As a result, when SMP is disabled, the generic definition is used, and riscv_isa gets initialized based on the ISA string of hart 0, not the boot hart. On FU740, this means has_fpu() returns false, and userspace crashes when trying to use floating-point instructions. Fix this by moving arch_match_cpu_phys_id() to a file which is always compiled. Fixes:70114560b2("RISC-V: Add RISC-V specific arch_match_cpu_phys_id") Fixes:914d6f44fc("RISC-V: only iterate over possible CPUs in ISA string parser") Reported-by: Palmer Dabbelt <palmer@rivosinc.com> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Link: https://lore.kernel.org/r/20230803012608.3540081-1-samuel.holland@sifive.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.