The Linux kernel parses the ISA extensions from "riscv,isa" DT property. It used to parse only the single letter base extensions until now. A generic ISA extension parsing framework was proposed[1] recently that can parse multi-letter ISA extensions as well.
Generate the extended ISA string by appending the available ISA extensions to the "riscv,isa" string if it is enabled so that kernel can process it. [1] https://lkml.org/lkml/2022/2/15/263 Suggested-by: Heiko Stubner <he...@sntech.de> Signed-off-by: Atish Patra <ati...@rivosinc.com> --- Changes from v1->v2: 1. Improved the code redability by using arrays instead of individual check --- target/riscv/cpu.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c index b0a40b83e7a8..9bf8923f164b 100644 --- a/target/riscv/cpu.c +++ b/target/riscv/cpu.c @@ -34,6 +34,13 @@ /* RISC-V CPU definitions */ +/* This includes the null terminated character '\0' */ +#define MAX_ISA_EXT_LEN 256 +struct isa_ext_data { + const char *name; + bool enabled; +}; + static const char riscv_exts[26] = "IEMAFDQCLBJTPVNSUHKORWXYZG"; const char * const riscv_int_regnames[] = { @@ -881,10 +888,35 @@ static void riscv_cpu_class_init(ObjectClass *c, void *data) device_class_set_props(dc, riscv_cpu_properties); } +static void riscv_isa_string_ext(RISCVCPU *cpu, char *isa_str, int max_str_len) +{ + int offset = strnlen(isa_str, max_str_len); + int i; + struct isa_ext_data isa_edata_arr[] = { + { "svpbmt", cpu->cfg.ext_svpbmt }, + { "svinval", cpu->cfg.ext_svinval }, + { "svnapot", cpu->cfg.ext_svnapot }, + }; + + for (i = 0; i < ARRAY_SIZE(isa_edata_arr); i++) { + if (!isa_edata_arr[i].enabled) { + continue; + } + /* check available space */ + if ((offset + strlen(isa_edata_arr[i].name) + 1) > max_str_len) { + qemu_log("No space left to append isa extension"); + return; + } + offset += snprintf(isa_str + offset, max_str_len, "_%s", + isa_edata_arr[i].name); + } +} + char *riscv_isa_string(RISCVCPU *cpu) { int i; - const size_t maxlen = sizeof("rv128") + sizeof(riscv_exts) + 1; + const size_t maxlen = sizeof("rv128") + sizeof(riscv_exts) + + MAX_ISA_EXT_LEN; char *isa_str = g_new(char, maxlen); char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS); for (i = 0; i < sizeof(riscv_exts); i++) { @@ -893,6 +925,7 @@ char *riscv_isa_string(RISCVCPU *cpu) } } *p = '\0'; + riscv_isa_string_ext(cpu, isa_str, maxlen); return isa_str; } -- 2.30.2