diff options
author | Jisheng Zhang <jszhang@kernel.org> | 2023-12-25 12:42:07 +0800 |
---|---|---|
committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-01-09 20:18:20 -0800 |
commit | d0fdc20b0429150c9dd09111f9b1d9d48117b56f (patch) | |
tree | 93429751a6d0d27648e673c032c1d6555b312ca2 /arch/riscv/mm/extable.c | |
parent | b6da6cbe13ebf24716438de71d50573b9f36f35d (diff) |
riscv: select DCACHE_WORD_ACCESS for efficient unaligned access HW
DCACHE_WORD_ACCESS uses the word-at-a-time API for optimised string
comparisons in the vfs layer.
This patch implements support for load_unaligned_zeropad in much the
same way as has been done for arm64.
Here is the test program and step:
$ cat tt.c
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#define ITERATIONS 1000000
#define PATH "123456781234567812345678123456781"
int main(void)
{
unsigned long i;
struct stat buf;
for (i = 0; i < ITERATIONS; i++)
stat(PATH, &buf);
return 0;
}
$ gcc -O2 tt.c
$ touch 123456781234567812345678123456781
$ time ./a.out
Per my test on T-HEAD C910 platforms, the above test performance is
improved by about 7.5%.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20231225044207.3821-3-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/mm/extable.c')
-rw-r--r-- | arch/riscv/mm/extable.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c index 35484d830fd6..dd1530af3ef1 100644 --- a/arch/riscv/mm/extable.c +++ b/arch/riscv/mm/extable.c @@ -27,6 +27,14 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex, return true; } +static inline unsigned long regs_get_gpr(struct pt_regs *regs, unsigned int offset) +{ + if (unlikely(!offset || offset > MAX_REG_OFFSET)) + return 0; + + return *(unsigned long *)((unsigned long)regs + offset); +} + static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset, unsigned long val) { @@ -50,6 +58,27 @@ static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, return true; } +static bool +ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, + struct pt_regs *regs) +{ + int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data); + int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); + unsigned long data, addr, offset; + + addr = regs_get_gpr(regs, reg_addr * sizeof(unsigned long)); + + offset = addr & 0x7UL; + addr &= ~0x7UL; + + data = *(unsigned long *)addr >> (offset * 8); + + regs_set_gpr(regs, reg_data * sizeof(unsigned long), data); + + regs->epc = get_ex_fixup(ex); + return true; +} + bool fixup_exception(struct pt_regs *regs) { const struct exception_table_entry *ex; @@ -65,6 +94,8 @@ bool fixup_exception(struct pt_regs *regs) return ex_handler_bpf(ex, regs); case EX_TYPE_UACCESS_ERR_ZERO: return ex_handler_uaccess_err_zero(ex, regs); + case EX_TYPE_LOAD_UNALIGNED_ZEROPAD: + return ex_handler_load_unaligned_zeropad(ex, regs); } BUG(); |