riscv: introduce unified static key mechanism for ISA extensions
Currently, riscv has several extensions which may not be supported on all riscv platforms, for example, FPU and so on. To support unified kernel Image style, we need to check whether the feature is supported or not. If the check sits at hot code path, then performance will be impacted a lot. static key can be used to solve the issue. In the past, FPU support has been converted to use static key mechanism. I believe we will have similar cases in the future. This patch tries to add an unified mechanism to use static keys for some ISA extensions by implementing an array of default-false static keys and enabling them when detected. Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Reviewed-by: Atish Patra <atishp@rivosinc.com> Reviewed-by: Anup Patel <anup@brainfault.org> Link: https://lore.kernel.org/r/20220522153543.2656-2-jszhang@kernel.orgSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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