diff options
| -rw-r--r-- | arch/riscv/kernel/cpu.c | 49 |
1 files changed, 36 insertions, 13 deletions
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c index fa427bdcf773..4480c2833ecc 100644 --- a/arch/riscv/kernel/cpu.c +++ b/arch/riscv/kernel/cpu.c @@ -120,22 +120,45 @@ device_initcall(riscv_cpuinfo_init); .uprop = #UPROP, \ .isa_ext_id = EXTID, \ } + /* - * Here are the ordering rules of extension naming defined by RISC-V - * specification : - * 1. All extensions should be separated from other multi-letter extensions - * by an underscore. - * 2. The first letter following the 'Z' conventionally indicates the most + * The canonical order of ISA extension names in the ISA string is defined in + * chapter 27 of the unprivileged specification. + * + * Ordinarily, for in-kernel data structures, this order is unimportant but + * isa_ext_arr defines the order of the ISA string in /proc/cpuinfo. + * + * The specification uses vague wording, such as should, when it comes to + * ordering, so for our purposes the following rules apply: + * + * 1. All multi-letter extensions must be separated from other extensions by an + * underscore. + * + * 2. Additional standard extensions (starting with 'Z') must be sorted after + * single-letter extensions and before any higher-privileged extensions. + + * 3. The first letter following the 'Z' conventionally indicates the most * closely related alphabetical extension category, IMAFDQLCBKJTPVH. - * If multiple 'Z' extensions are named, they should be ordered first - * by category, then alphabetically within a category. - * 3. Standard supervisor-level extensions (starts with 'S') should be - * listed after standard unprivileged extensions. If multiple - * supervisor-level extensions are listed, they should be ordered + * If multiple 'Z' extensions are named, they must be ordered first by + * category, then alphabetically within a category. + * + * 3. Standard supervisor-level extensions (starting with 'S') must be listed + * after standard unprivileged extensions. If multiple supervisor-level + * extensions are listed, they must be ordered alphabetically. + * + * 4. Standard machine-level extensions (starting with 'Zxm') must be listed + * after any lower-privileged, standard extensions. If multiple + * machine-level extensions are listed, they must be ordered * alphabetically. - * 4. Non-standard extensions (starts with 'X') must be listed after all - * standard extensions. They must be separated from other multi-letter - * extensions by an underscore. + * + * 5. Non-standard extensions (starting with 'X') must be listed after all + * standard extensions. If multiple non-standard extensions are listed, they + * must be ordered alphabetically. + * + * An example string following the order is: + * rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux + * + * New entries to this struct should follow the ordering rules described above. */ static struct riscv_isa_ext_data isa_ext_arr[] = { __RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF), |