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Message-ID: <20251021-01a9b77e3d88543581f1a7fb@orel>
Date: Tue, 21 Oct 2025 16:32:40 -0700
From: Andrew Jones <ajones@...tanamicro.com>
To: Yao Zihong <zihong.plct@...c.iscas.ac.cn>
Cc: alex@...ti.fr, alexghiti@...osinc.com, aou@...s.berkeley.edu,
cleger@...osinc.com, evan@...osinc.com, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, palmer@...belt.com, pjw@...nel.org, samuel.holland@...ive.com,
shuah@...nel.org, zhangyin2018@...as.ac.cn, zihongyao@...look.com
Subject: Re: [PATCH v3 2/2] selftests/riscv: Add Zicbop prefetch test
On Mon, Oct 20, 2025 at 11:37:20PM +0800, Yao Zihong wrote:
> Add selftest to cbo.c to verify Zicbop extension behavior.
>
> The test checks:
> - That hwprobe correctly reports Zicbop presence and block size.
> - That prefetch instructions execute without exception on valid and NULL
> addresses when Zicbop is present.
> - That prefetch.{i,r,w} do not trigger SIGILL even when Zicbop is absent,
> since Zicbop instructions are defined as hints.
>
> Signed-off-by: Yao Zihong <zihong.plct@...c.iscas.ac.cn>
> ---
> tools/testing/selftests/riscv/hwprobe/cbo.c | 188 +++++++++++++++++---
> 1 file changed, 159 insertions(+), 29 deletions(-)
>
> diff --git a/tools/testing/selftests/riscv/hwprobe/cbo.c b/tools/testing/selftests/riscv/hwprobe/cbo.c
> index 5e96ef785d0d..163228e3f2c7 100644
> --- a/tools/testing/selftests/riscv/hwprobe/cbo.c
> +++ b/tools/testing/selftests/riscv/hwprobe/cbo.c
> @@ -15,24 +15,30 @@
> #include <linux/compiler.h>
> #include <linux/kernel.h>
> #include <asm/ucontext.h>
> +#include <getopt.h>
>
> #include "hwprobe.h"
> #include "../../kselftest.h"
>
> #define MK_CBO(fn) le32_bswap((uint32_t)(fn) << 20 | 10 << 15 | 2 << 12 | 0 << 7 | 15)
> +#define MK_PREFETCH(fn) \
> + le32_bswap(0 << 25 | (uint32_t)(fn) << 20 | 10 << 15 | 6 << 12 | 0 << 7 | 19)
>
> static char mem[4096] __aligned(4096) = { [0 ... 4095] = 0xa5 };
>
> -static bool illegal_insn;
> +static bool got_fault;
>
> static void sigill_handler(int sig, siginfo_t *info, void *context)
> {
> unsigned long *regs = (unsigned long *)&((ucontext_t *)context)->uc_mcontext;
> uint32_t insn = *(uint32_t *)regs[0];
>
> - assert(insn == MK_CBO(regs[11]));
> + if (regs[12] == 0)
> + assert(insn == MK_CBO(regs[11]));
> + else
> + assert(insn == MK_PREFETCH(regs[11]));
>
> - illegal_insn = true;
> + got_fault = true;
> regs[0] += 4;
> }
>
> @@ -41,43 +47,75 @@ static void sigill_handler(int sig, siginfo_t *info, void *context)
> asm volatile( \
> "mv a0, %0\n" \
> "li a1, %1\n" \
> + "li a2, 0\n" \
> ".4byte %2\n" \
> - : : "r" (base), "i" (fn), "i" (MK_CBO(fn)) : "a0", "a1", "memory"); \
> + : : "r" (base), "i" (fn), "i" (MK_CBO(fn)) : "a0", "a1", "a2", "memory"); \
> +})
> +
> +#define prefetch_insn(base, fn) \
> +({ \
> + asm volatile( \
> + "mv a0, %0\n" \
> + "li a1, %1\n" \
> + "li a2, 1\n" \
> + ".4byte %2\n" \
> + : : "r" (base), "i" (fn), "i" (MK_PREFETCH(fn)) : "a0", "a1", "a2");\
> })
>
> static void cbo_inval(char *base) { cbo_insn(base, 0); }
> static void cbo_clean(char *base) { cbo_insn(base, 1); }
> static void cbo_flush(char *base) { cbo_insn(base, 2); }
> static void cbo_zero(char *base) { cbo_insn(base, 4); }
> +static void prefetch_i(char *base) { prefetch_insn(base, 0); }
> +static void prefetch_r(char *base) { prefetch_insn(base, 1); }
> +static void prefetch_w(char *base) { prefetch_insn(base, 3); }
> +
> +static void test_no_zicbop(void *arg)
> +{
> + /* Zicbop prefetch.* are HINT instructions. */
> + ksft_print_msg("Testing Zicbop instructions\n");
> +
> + got_fault = false;
> + prefetch_i(&mem[0]);
> + ksft_test_result(!got_fault, "No prefetch.i\n");
> +
> + got_fault = false;
> + prefetch_r(&mem[0]);
> + ksft_test_result(!got_fault, "No prefetch.r\n");
> +
> + got_fault = false;
> + prefetch_w(&mem[0]);
> + ksft_test_result(!got_fault, "No prefetch.w\n");
> +}
>
> static void test_no_cbo_inval(void *arg)
> {
> ksft_print_msg("Testing cbo.inval instruction remain privileged\n");
> - illegal_insn = false;
> + got_fault = false;
> cbo_inval(&mem[0]);
> - ksft_test_result(illegal_insn, "No cbo.inval\n");
> + ksft_test_result(got_fault, "No cbo.inval\n");
> }
>
> static void test_no_zicbom(void *arg)
> {
> ksft_print_msg("Testing Zicbom instructions remain privileged\n");
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_clean(&mem[0]);
> - ksft_test_result(illegal_insn, "No cbo.clean\n");
> + ksft_test_result(got_fault, "No cbo.clean\n");
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_flush(&mem[0]);
> - ksft_test_result(illegal_insn, "No cbo.flush\n");
> + ksft_test_result(got_fault, "No cbo.flush\n");
> }
>
> static void test_no_zicboz(void *arg)
> {
> ksft_print_msg("No Zicboz, testing cbo.zero remains privileged\n");
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_zero(&mem[0]);
> - ksft_test_result(illegal_insn, "No cbo.zero\n");
> + ksft_test_result(got_fault, "No cbo.zero\n");
> }
>
> static bool is_power_of_2(__u64 n)
> @@ -85,6 +123,34 @@ static bool is_power_of_2(__u64 n)
> return n != 0 && (n & (n - 1)) == 0;
> }
>
> +static void test_zicbop(void *arg)
> +{
> + struct riscv_hwprobe pair = {
> + .key = RISCV_HWPROBE_KEY_ZICBOP_BLOCK_SIZE,
> + };
> + cpu_set_t *cpus = (cpu_set_t *)arg;
> + __u64 block_size;
> + long rc;
> +
> + rc = riscv_hwprobe(&pair, 1, sizeof(cpu_set_t), (unsigned long *)cpus, 0);
> + block_size = pair.value;
> + ksft_test_result(rc == 0 && pair.key == RISCV_HWPROBE_KEY_ZICBOP_BLOCK_SIZE &&
> + is_power_of_2(block_size), "Zicbop block size\n");
> + ksft_print_msg("Zicbop block size: %llu\n", block_size);
> +
> + got_fault = false;
> + prefetch_i(&mem[0]);
> + prefetch_r(&mem[0]);
> + prefetch_w(&mem[0]);
> + ksft_test_result(!got_fault, "Zicbop prefetch.* on valid address\n");
> +
> + got_fault = false;
> + prefetch_i(NULL);
> + prefetch_r(NULL);
> + prefetch_w(NULL);
> + ksft_test_result(!got_fault, "Zicbop prefetch.* on NULL\n");
> +}
> +
> static void test_zicbom(void *arg)
> {
> struct riscv_hwprobe pair = {
> @@ -100,13 +166,13 @@ static void test_zicbom(void *arg)
> is_power_of_2(block_size), "Zicbom block size\n");
> ksft_print_msg("Zicbom block size: %llu\n", block_size);
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_clean(&mem[block_size]);
> - ksft_test_result(!illegal_insn, "cbo.clean\n");
> + ksft_test_result(!got_fault, "cbo.clean\n");
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_flush(&mem[block_size]);
> - ksft_test_result(!illegal_insn, "cbo.flush\n");
> + ksft_test_result(!got_fault, "cbo.flush\n");
> }
>
> static void test_zicboz(void *arg)
> @@ -125,11 +191,11 @@ static void test_zicboz(void *arg)
> is_power_of_2(block_size), "Zicboz block size\n");
> ksft_print_msg("Zicboz block size: %llu\n", block_size);
>
> - illegal_insn = false;
> + got_fault = false;
> cbo_zero(&mem[block_size]);
> - ksft_test_result(!illegal_insn, "cbo.zero\n");
> + ksft_test_result(!got_fault, "cbo.zero\n");
>
> - if (illegal_insn || !is_power_of_2(block_size)) {
> + if (got_fault || !is_power_of_2(block_size)) {
> ksft_test_result_skip("cbo.zero check\n");
> return;
> }
> @@ -148,7 +214,7 @@ static void test_zicboz(void *arg)
> if (mem[i * block_size + j] != expected) {
> ksft_test_result_fail("cbo.zero check\n");
> ksft_print_msg("cbo.zero check: mem[%llu] != 0x%x\n",
> - i * block_size + j, expected);
> + i * block_size + j, expected);
Undesired reformatting
> return;
> }
> }
> @@ -177,7 +243,19 @@ static void check_no_zicbo_cpus(cpu_set_t *cpus, __u64 cbo)
> rc = riscv_hwprobe(&pair, 1, sizeof(cpu_set_t), (unsigned long *)&one_cpu, 0);
> assert(rc == 0 && pair.key == RISCV_HWPROBE_KEY_IMA_EXT_0);
>
> - cbostr = cbo == RISCV_HWPROBE_EXT_ZICBOZ ? "Zicboz" : "Zicbom";
> + switch (cbo) {
> + case RISCV_HWPROBE_EXT_ZICBOZ:
> + cbostr = "Zicboz";
> + break;
> + case RISCV_HWPROBE_EXT_ZICBOM:
> + cbostr = "Zicbom";
> + break;
> + case RISCV_HWPROBE_EXT_ZICBOP:
> + cbostr = "Zicbop";
> + break;
> + default:
> + ksft_exit_fail_msg("Internal error: invalid cbo %llu\n", cbo);
> + }
>
> if (pair.value & cbo)
> ksft_exit_fail_msg("%s is only present on a subset of harts.\n"
> @@ -194,6 +272,8 @@ enum {
> TEST_ZICBOM,
> TEST_NO_ZICBOM,
> TEST_NO_CBO_INVAL,
> + TEST_ZICBOP,
> + TEST_NO_ZICBOP
> };
>
> static struct test_info {
> @@ -206,27 +286,70 @@ static struct test_info {
> [TEST_ZICBOM] = { .nr_tests = 3, test_zicbom },
> [TEST_NO_ZICBOM] = { .nr_tests = 2, test_no_zicbom },
> [TEST_NO_CBO_INVAL] = { .nr_tests = 1, test_no_cbo_inval },
> + [TEST_ZICBOP] = { .nr_tests = 3, test_zicbop },
> + [TEST_NO_ZICBOP] = { .nr_tests = 3, test_no_zicbop },
> };
>
> -int main(int argc, char **argv)
> +static const struct option long_opts[] = {
> + {"sigill", no_argument, 0, 'i'},
> + {"sigsegv", no_argument, 0, 's'},
> + {"sigbus", no_argument, 0, 'b'},
> + {0, 0, 0, 0}
> +};
> +
> +static void install_sigaction(int argc, char **argv)
> {
> + int rc, opt, long_index;
> + bool sigill;
> +
> struct sigaction act = {
> .sa_sigaction = &sigill_handler,
> .sa_flags = SA_SIGINFO,
> };
> +
> + long_index = 0;
> + sigill = false;
> +
> + while ((opt = getopt_long(argc, argv, "isb", long_opts, &long_index)) != -1) {
> + switch (opt) {
> + case 'i':
> + rc = sigaction(SIGILL, &act, NULL);
> + assert(rc == 0);
> + sigill = true;
> + break;
> + case 's':
> + rc = sigaction(SIGSEGV, &act, NULL);
> + assert(rc == 0);
> + break;
> + case 'b':
> + rc = sigaction(SIGBUS, &act, NULL);
> + assert(rc == 0);
> + break;
Should we just unconditionally register handlers for SIGSEGV and SIGBUS?
> + case '?':
> + fprintf(stderr, "Unknown option or missing arg\n");
> + exit(1);
> + default:
> + break;
> + }
> + }
> +
> + if (sigill) {
> + tests[TEST_NO_ZICBOZ].enabled = true;
> + tests[TEST_NO_ZICBOM].enabled = true;
> + tests[TEST_NO_CBO_INVAL].enabled = true;
> + tests[TEST_NO_ZICBOP].enabled = true;
> + }
> +}
> +
> +int main(int argc, char **argv)
> +{
> struct riscv_hwprobe pair;
> unsigned int plan = 0;
> cpu_set_t cpus;
> long rc;
> int i;
>
> - if (argc > 1 && !strcmp(argv[1], "--sigill")) {
> - rc = sigaction(SIGILL, &act, NULL);
> - assert(rc == 0);
> - tests[TEST_NO_ZICBOZ].enabled = true;
> - tests[TEST_NO_ZICBOM].enabled = true;
> - tests[TEST_NO_CBO_INVAL].enabled = true;
> - }
> + install_sigaction(argc, argv);
>
> rc = sched_getaffinity(0, sizeof(cpu_set_t), &cpus);
> assert(rc == 0);
> @@ -253,6 +376,13 @@ int main(int argc, char **argv)
> check_no_zicbo_cpus(&cpus, RISCV_HWPROBE_EXT_ZICBOM);
> }
>
> + if (pair.value & RISCV_HWPROBE_EXT_ZICBOP) {
> + tests[TEST_ZICBOP].enabled = true;
> + tests[TEST_NO_ZICBOP].enabled = false;
> + } else {
> + check_no_zicbo_cpus(&cpus, RISCV_HWPROBE_EXT_ZICBOP);
> + }
> +
> for (i = 0; i < ARRAY_SIZE(tests); ++i)
> plan += tests[i].enabled ? tests[i].nr_tests : 0;
>
> --
> 2.47.2
>
Otherwise
Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
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