Nathan Lynch via B4 Relay [off-list ref]
writes:

From: Nathan Lynch <redacted>

Consistently testing system parameter access is a bit difficult by
nature -- the set of parameters available depends on the model and
system configuration, and updating a parameter should be considered a
destructive operation reserved for the admin.

...

...

+static int set_hmc0(void)
+{
+	struct papr_sysparm_io_block sp = {
+		.parameter = 0, // HMC0, not a settable parameter
+	};
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	// Ensure expected error
+	FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_SET, &sp) != -1);
+	FAIL_IF(errno != EPERM);
+
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}

This one fails when run with qemu/KVM.

# selftests: powerpc: papr_sysparm
# test: open and close /dev/papr-sysparm without issuing commands
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# success: open and close /dev/papr-sysparm without issuing commands
# test: retrieve SPLPAR characteristics
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# success: retrieve SPLPAR characteristics
# test: verify EOPNOTSUPP for known-bad parameter
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# success: verify EOPNOTSUPP for known-bad parameter
# test: PAPR_SYSPARM_IOC_GET returns EFAULT on bad address
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# success: PAPR_SYSPARM_IOC_GET returns EFAULT on bad address
# test: PAPR_SYSPARM_IOC_SET returns EFAULT on bad address
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# success: PAPR_SYSPARM_IOC_SET returns EFAULT on bad address
# test: ensure EPERM on attempt to update HMC0
# tags: git_version:v6.7-rc2-35-g41ada9f713ae
# [FAIL] Test FAILED on line 113
# failure: ensure EPERM on attempt to update HMC0

It's returning EOPNOTSUPP.

Something like below would work to fix it.

cheers

diff --git a/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c b/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c
index fc25c03e8bc7..9d4850c25aed 100644
--- a/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c
+++ b/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c

@@ -110,6 +110,7 @@ static int set_hmc0(void)

        // Ensure expected error
        FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_SET, &sp) != -1);
+       SKIP_IF_MSG(errno == EOPNOTSUPP, "operation not supported");
        FAIL_IF(errno != EPERM);

        FAIL_IF(close(devfd) != 0);