KVM: arm64: selftests: Test ID_AA64PFR0.MPAM isn't completely ignored
The ID_AA64PFR0.MPAM bit was previously accidentally exposed to guests,
and is ignored by KVM. KVM will always present the guest with 0 here,
and trap the MPAM system registers to inject an undef.
But, this vaulue is still needed to prevent migration when the value
is incompatible with the target hardware. Add a kvm unit test to try
and write multiple values to ID_AA64PFR0.MPAM. Only the hardware value
previously exposed should be ignored, all other values should be
rejected.
Signed-off-by: James Morse <james.morse@arm.com>
diff --git a/tools/testing/selftests/kvm/aarch64/set_id_regs.c b/tools/testing/selftests/kvm/aarch64/set_id_regs.c
index b42a0dc1..fbb6001 100644
--- a/tools/testing/selftests/kvm/aarch64/set_id_regs.c
+++ b/tools/testing/selftests/kvm/aarch64/set_id_regs.c
@@ -426,6 +426,56 @@
}
}
+#define MPAM_IDREG_TEST 1
+static void test_user_set_mpam_reg(struct kvm_vcpu *vcpu)
+{
+ uint64_t masks[KVM_ARM_FEATURE_ID_RANGE_SIZE];
+ struct reg_mask_range range = {
+ .addr = (__u64)masks,
+ };
+ uint64_t val, ftr_mask;
+ int idx, err;
+
+ /*
+ * If ID_AA64PFR0.MPAM is _not_ officially modifiable and is zero,
+ * check that if it can be set to 1, (i.e. it is supported by the
+ * hardware), that it can't be set to other values.
+ */
+
+ /* Get writable masks for feature ID registers */
+ memset(range.reserved, 0, sizeof(range.reserved));
+ vm_ioctl(vcpu->vm, KVM_ARM_GET_REG_WRITABLE_MASKS, &range);
+
+ /* Writeable? Nothing to test! */
+ idx = sys_reg_to_idx(SYS_ID_AA64PFR0_EL1);
+ ftr_mask = ID_AA64PFR0_EL1_MPAM_MASK;
+ if ((masks[idx] & ftr_mask) == ftr_mask) {
+ ksft_test_result_skip("ID_AA64PFR0.MPAM is officially writable, nothing to test\n");
+ return;
+ }
+
+ /* Get the id register value */
+ vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64PFR0_EL1), &val);
+
+ /* Try to set MPAM=1 */
+ val &= ~GENMASK_ULL(44, 40);
+ val |= FIELD_PREP(GENMASK_ULL(44, 40), 1);
+ err = __vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64PFR0_EL1), val);
+ if (err) {
+ ksft_test_result_skip("ID_AA64PFR0.MPAM is not writable, nothing to test\n");
+ return;
+ }
+
+ /* Try to set MPAM=2 */
+ val &= ~GENMASK_ULL(43, 40);
+ val |= FIELD_PREP(GENMASK_ULL(43, 40), 2);
+ err = __vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64PFR0_EL1), val);
+ if (err == -EPERM)
+ ksft_test_result_pass("ID_AA64PFR0_EL1.MPAM not arbitrarily modifiable\n");
+ else
+ ksft_test_result_fail("ID_AA64PFR0_EL1.MPAM value should not be ignored\n");
+}
+
static void test_guest_reg_read(struct kvm_vcpu *vcpu)
{
bool done = false;
@@ -477,12 +527,13 @@
ARRAY_SIZE(ftr_id_aa64isar2_el1) + ARRAY_SIZE(ftr_id_aa64pfr0_el1) +
ARRAY_SIZE(ftr_id_aa64mmfr0_el1) + ARRAY_SIZE(ftr_id_aa64mmfr1_el1) +
ARRAY_SIZE(ftr_id_aa64mmfr2_el1) + ARRAY_SIZE(ftr_id_aa64zfr0_el1) -
- ARRAY_SIZE(test_regs);
+ ARRAY_SIZE(test_regs) + MPAM_IDREG_TEST;
ksft_set_plan(ftr_cnt);
test_user_set_reg(vcpu, aarch64_only);
test_guest_reg_read(vcpu);
+ test_user_set_mpam_reg(vcpu);
kvm_vm_free(vm);
