Re: [v1, 2/2] selftests: Test RISC-V Vector's first-use handler

["Björn Töpel" <bjorn@kernel.org>]

Andy Chiu <andy.chiu@sifive.com> writes:

> This add a test to check if the kernel zero-initializes all V registers
> after the first-use trap handler returns.
>
> If V registers are not zero-initialized, then the test should fail one
> out of several runs:
>
> ```
>  root@sifive-fpga:~# ./v_initval_nolibc
>  # vl = 256
>  not ok 1 detect stale values on v-regesters
>  0 0 0 0 0 0 0 0   0 0 0 0 0 0 0 0
>  0 4c 41 4e 47 3d 43 0   50 41 54 48 3d 2f 75 73
>  72 2f 6c 6f 63 61 6c 2f   73 62 69 6e 3a 2f 75 73
>  72 2f 6c 6f 63 61 6c 2f   62 69 6e 3a 2f 75 73 72
>  ff ff 81 0 0 0 0 0   0 0 0 0 0 0 0 0
> ```
>
> Otherwise, the test passes without errors each run.
>
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> ---
>  .../testing/selftests/riscv/vector/.gitignore |  1 +
>  tools/testing/selftests/riscv/vector/Makefile |  6 +-
>  .../selftests/riscv/vector/v_initval_nolibc.c | 68 +++++++++++++++++++
>  3 files changed, 74 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/riscv/vector/v_initval_nolibc.c
>
> diff --git a/tools/testing/selftests/riscv/vector/.gitignore b/tools/testing/selftests/riscv/vector/.gitignore
> index 4f2b4e8a3b08..9ae7964491d5 100644
> --- a/tools/testing/selftests/riscv/vector/.gitignore
> +++ b/tools/testing/selftests/riscv/vector/.gitignore
> @@ -1,2 +1,3 @@
>  vstate_exec_nolibc
>  vstate_prctl
> +v_initval_nolibc
> diff --git a/tools/testing/selftests/riscv/vector/Makefile b/tools/testing/selftests/riscv/vector/Makefile
> index cd6e80bf995d..bfff0ff4f3be 100644
> --- a/tools/testing/selftests/riscv/vector/Makefile
> +++ b/tools/testing/selftests/riscv/vector/Makefile
> @@ -2,7 +2,7 @@
>  # Copyright (C) 2021 ARM Limited
>  # Originally tools/testing/arm64/abi/Makefile
>  
> -TEST_GEN_PROGS := vstate_prctl
> +TEST_GEN_PROGS := vstate_prctl v_initval_nolibc
>  TEST_GEN_PROGS_EXTENDED := vstate_exec_nolibc
>  
>  include ../../lib.mk
> @@ -13,3 +13,7 @@ $(OUTPUT)/vstate_prctl: vstate_prctl.c ../hwprobe/sys_hwprobe.S
>  $(OUTPUT)/vstate_exec_nolibc: vstate_exec_nolibc.c
>  	$(CC) -nostdlib -static -include ../../../../include/nolibc/nolibc.h \
>  		-Wall $(CFLAGS) $(LDFLAGS) $^ -o $@ -lgcc
> +
> +$(OUTPUT)/v_initval_nolibc: v_initval_nolibc.c
> +	$(CC) -nostdlib -static -include ../../../../include/nolibc/nolibc.h \
> +		-Wall $(CFLAGS) $(LDFLAGS) $^ -o $@ -lgcc

Hmm, does this build with clang? (No, bigge on my end, and can be fixed
later.)

> diff --git a/tools/testing/selftests/riscv/vector/v_initval_nolibc.c b/tools/testing/selftests/riscv/vector/v_initval_nolibc.c
> new file mode 100644
> index 000000000000..66764edb0d52
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/vector/v_initval_nolibc.c
> @@ -0,0 +1,68 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include "../../kselftest.h"
> +#define MAX_VSIZE	(8192 * 32)
> +
> +void dump(char *ptr, int size)
> +{
> +	int i = 0;
> +
> +	for (i = 0; i < size; i++) {
> +		if (i != 0) {
> +			if (i % 16 == 0)
> +				printf("\n");
> +			else if (i % 8 == 0)
> +				printf("  ");
> +		}
> +		printf("%02x ", ptr[i]);
> +	}
> +	printf("\n");
> +}
> +
> +int main(void)
> +{
> +	int i;
> +	unsigned long vl;
> +	char *datap, *tmp;
> +
> +	datap = malloc(MAX_VSIZE);
> +	if (!datap) {
> +		ksft_test_result_fail("fail to allocate memory for size = %lu\n", MAX_VSIZE);
> +		exit(-1);
> +	}
> +
> +	tmp = datap;
> +	asm volatile (
> +		".option push\n\t"
> +		".option arch, +v\n\t"
> +		"vsetvli	%0, x0, e8, m8, ta, ma\n\t"
> +		"vse8.v		v0, (%2)\n\t"
> +		"add		%1, %2, %0\n\t"
> +		"vse8.v		v8, (%1)\n\t"
> +		"add		%1, %1, %0\n\t"
> +		"vse8.v		v16, (%1)\n\t"
> +		"add		%1, %1, %0\n\t"
> +		"vse8.v		v24, (%1)\n\t"
> +		".option pop\n\t"
> +		: "=&r" (vl), "=r" (tmp) : "r" (datap) : "memory");
> +
> +	ksft_print_msg("vl = %lu\n", vl);
> +
> +	if (datap[0] != 0x00 && datap[0] != 0xff) {
> +		ksft_test_result_fail("v-regesters are not properly initialized\n");

Nit: "v-registers"

> +		dump(datap, vl * 4);
> +		exit(-1);
> +	}
> +
> +	for (i = 1; i < vl * 4; i++) {
> +		if (datap[i] != datap[0]) {
> +			ksft_test_result_fail("detect stale values on v-regesters\n");

Nit (dito): "v-registers", and maybe "detected".


With, or without the changes above,
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>

Björn

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