Messages in this thread | | | Date | Thu, 3 Aug 2023 07:26:08 +0100 | From | Conor Dooley <> | Subject | Re: [PATCH] riscv: Fix CPU feature detection with SMP disabled |
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On Wed, Aug 02, 2023 at 06:26:06PM -0700, Samuel Holland wrote: > commit 914d6f44fc50 ("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.)
Ouch, that I did not realise. Should we revert that portion of the changes? Starting to sound like we should..
> 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: 70114560b285 ("RISC-V: Add RISC-V specific arch_match_cpu_phys_id") > Fixes: 914d6f44fc50 ("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>
Thanks for fixing this Samuel. [unhandled content-type:application/pgp-signature] | |