kselftest/arm64: Specify SVE data when testing VL set in sve-ptrace

Since f916dd3 ("arm64/fpsimd: ptrace: Mandate SVE payload for
streaming-mode state") we reject attempts to write to the streaming mode
regset even if there is no register data supplied, causing the tests for
setting vector lengths and setting SVE_VL_INHERIT in sve-ptrace to
spuriously fail. Set the flag to avoid the issue, we still support not
supplying register data.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250609-kselftest-arm64-ssve-fixups-v2-3-998fcfa6f240@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: broonie

tools/testing/selftests/arm64/fp/sve-ptrace.c

@@ -170,7 +170,7 @@ static void ptrace_set_get_inherit(pid_t child, const struct vec_type *type)
 	memset(&sve, 0, sizeof(sve));
 	sve.size = sizeof(sve);
 	sve.vl = sve_vl_from_vq(SVE_VQ_MIN);
-	sve.flags = SVE_PT_VL_INHERIT;
+	sve.flags = SVE_PT_VL_INHERIT | SVE_PT_REGS_SVE;
 	ret = set_sve(child, type, &sve);
 	if (ret != 0) {
 		ksft_test_result_fail("Failed to set %s SVE_PT_VL_INHERIT\n",
@@ -235,6 +235,7 @@ static void ptrace_set_get_vl(pid_t child, const struct vec_type *type,
 	/* Set the VL by doing a set with no register payload */
 	memset(&sve, 0, sizeof(sve));
 	sve.size = sizeof(sve);
+	sve.flags = SVE_PT_REGS_SVE;
 	sve.vl = vl;
 	ret = set_sve(child, type, &sve);
 	if (ret != 0) {