From: Ruinland ChuanTzu Tsai <ruinl...@andestech.com> Dear all,
In this patch, the implementation of custom CSR handling logic is introduced. If --enable-riscv-custom is set during configuration, custom CSR logic will be turned on. During CPU model initialization, setup_custom_csr() is invoked to register vendor-provided custom CSR opsets into a hash table. When accessing a CSR, in riscv_csrrw(), is_custom_csr() will be called to check whether the encountering csrno is a custom CSR. If that's a custom one, a struct riscv_csr_operations will be returned and such CSR will be served accordingly. The performance slowdown could be easily tested with a simple program running on linux-user mode. /* test_csr.c */ #include <stdio.h> #include <unistd.h> #include <sys/time.h> int main (int ac, char *av[]) { struct timeval start; struct timeval end; gettimeofday(&start,NULL); unsigned int loop_n = 999999 ; unsigned char i; unsigned char o; do { for(i=0; i<32; i++) { #if defined(FCSR) __asm__("csrw fcsr, %0;"::"r"(i)); __asm__("csrr %0, fcsr;":"=r"(o)); #elif defined(UITB) __asm__("csrw 0x800, %0;"::"r"(i)); __asm__("csrr %0, 0x800;":"=r"(o)); #endif } --loop_n; } while (loop_n > 0); gettimeofday(&end,NULL); unsigned long diff = 1000000 * (end.tv_sec-start.tv_sec)+end.tv_usec-start.tv_usec; printf("%f\n", (double)(diff)/1000000); return 0; } $ riscv64-linux-gnu-gcc -static -DUITB ./test_csr.c -o ./u $ riscv64-linux-gnu-gcc -static -DFCSR ./test_csr.c -o ./f For a custom CSR, uitb, being accessed on andes-ax25 : $ ./build/qemu-riscv64 -cpu andes-ax25 ./u 4.283091 For a stock CSR, fcsr, being accessed on andes-ax25: $ ./build/qemu-riscv64 ./f 3.875519 For a custom CSR being accessed on stock rv64: $ ./build/qemu-riscv64 -cpu rv64 ./u Illegal instruction (core dumped) # This is expected to fail. Currently, the statics on my hands shows that : When the custom CSR handling mechanism is activated, we will suffer a 17% slow- down on stock CSRs and the penalty of accessing to a custom CSR will be another 7% more. Cordially yours, Ruinland ChuanTzu Tsai Changes from v3 : * Adding options in configure and meson files to turn on/off custom CSR logic. * Adding unlikely() to check if custom_csr_map is set. * Moving any32 and any out of !(CONFIG_USER_ONLY) for enabling linux-user mode. * Fix comment style, add missing license boilerplate. Ruinalnd ChuanTzu Tsai (4): Adding basic custom/vendor CSR handling mechanism Adding Andes AX25 and A25 CPU model Enable custom CSR logic for Andes AX25 and A25 Add options to config/meson files for custom CSR configure | 6 ++ meson.build | 2 + meson_options.txt | 2 + target/riscv/andes_cpu_bits.h | 124 +++++++++++++++++++++++++ target/riscv/cpu.c | 51 +++++++++++ target/riscv/cpu.h | 33 ++++++- target/riscv/cpu_bits.h | 4 + target/riscv/csr.c | 83 ++++++++++++++--- target/riscv/csr_andes.inc.c | 160 +++++++++++++++++++++++++++++++++ target/riscv/custom_cpu_bits.h | 12 +++ 10 files changed, 462 insertions(+), 15 deletions(-) create mode 100644 target/riscv/andes_cpu_bits.h create mode 100644 target/riscv/csr_andes.inc.c create mode 100644 target/riscv/custom_cpu_bits.h -- 2.32.0