[PATCH 5/5] KVM: selftests: Add MONITOR/MWAIT quirk test

Sean Christopherson
2022-06-08T22:45:39Z

Add a test to verify the "MONITOR/MWAIT never fault" quirk, and as a
bonus, also verify the related "MISC_ENABLES ignores ENABLE_MWAIT" quirk.

If the "never fault" quirk is enabled, MONITOR/MWAIT should always be
emulated as NOPs, even if they're reported as disabled in guest CPUID.
Use the MISC_ENABLES quirk to coerce KVM into toggling the MWAIT CPUID
enable, as KVM now disallows manually toggling CPUID bits after running
the vCPU.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/x86_64/monitor_mwait_test.c | 127 ++++++++++++++++++
3 files changed, 129 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 0ab0e255d292..1a56522f009c 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -27,6 +27,7 @@
/x86_64/hyperv_svm_test
/x86_64/max_vcpuid_cap_test
/x86_64/mmio_warning_test
+/x86_64/monitor_mwait_test
/x86_64/platform_info_test
/x86_64/pmu_event_filter_test
/x86_64/set_boot_cpu_id
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 9a256c1f1bdf..bbbfdeb7ee9b 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -56,6 +56,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/hyperv_svm_test
TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_test
TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
+TEST_GEN_PROGS_x86_64 += x86_64/monitor_mwait_test
TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
TEST_GEN_PROGS_x86_64 += x86_64/pmu_event_filter_test
TEST_GEN_PROGS_x86_64 += x86_64/set_boot_cpu_id
diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
new file mode 100644
index 000000000000..b9af8e29721e
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "kvm_util.h"
+#include "processor.h"
+
+enum monitor_mwait_testcases {
+ MWAIT_QUIRK_DISABLED = BIT(0),
+ MISC_ENABLES_QUIRK_DISABLED = BIT(1),
+ MWAIT_DISABLED = BIT(2),
+};
+
+static void guest_monitor_wait(int testcase)
+{
+ /*
+ * If both MWAIT and its quirk are disabled, MONITOR/MWAIT should #UD,
+ * in all other scenarios KVM should emulate them as nops.
+ */
+ bool fault_wanted = (testcase & MWAIT_QUIRK_DISABLED) &&
+ (testcase & MWAIT_DISABLED);
+ u8 vector;
+
+ GUEST_SYNC(testcase);
+
+ vector = kvm_asm_safe("monitor");
+ if (fault_wanted)
+ GUEST_ASSERT_2(vector == UD_VECTOR, testcase, vector);
+ else
+ GUEST_ASSERT_2(!vector, testcase, vector);
+
+ vector = kvm_asm_safe("monitor");
+ if (fault_wanted)
+ GUEST_ASSERT_2(vector == UD_VECTOR, testcase, vector);
+ else
+ GUEST_ASSERT_2(!vector, testcase, vector);
+}
+
+static void guest_code(void)
+{
+ guest_monitor_wait(MWAIT_DISABLED);
+
+ guest_monitor_wait(MWAIT_QUIRK_DISABLED | MWAIT_DISABLED);
+
+ guest_monitor_wait(MISC_ENABLES_QUIRK_DISABLED | MWAIT_DISABLED);
+ guest_monitor_wait(MISC_ENABLES_QUIRK_DISABLED);
+
+ guest_monitor_wait(MISC_ENABLES_QUIRK_DISABLED | MWAIT_QUIRK_DISABLED | MWAIT_DISABLED);
+ guest_monitor_wait(MISC_ENABLES_QUIRK_DISABLED | MWAIT_QUIRK_DISABLED);
+
+ GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+ uint64_t disabled_quirks;
+ struct kvm_vcpu *vcpu;
+ struct kvm_run *run;
+ struct kvm_vm *vm;
+ struct ucall uc;
+ int testcase;
+
+ TEST_REQUIRE(kvm_has_cap(KVM_CAP_DISABLE_QUIRKS2));
+
+ vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+ vcpu_clear_cpuid_feature(vcpu, X86_FEATURE_MWAIT);
+
+ run = vcpu->run;
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(vcpu);
+
+ while (1) {
+ vcpu_run(vcpu);
+
+ TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+ "Unexpected exit reason: %u (%s),\n",
+ run->exit_reason,
+ exit_reason_str(run->exit_reason));
+
+ switch (get_ucall(vcpu, &uc)) {
+ case UCALL_SYNC:
+ testcase = uc.args[1];
+ break;
+ case UCALL_ABORT:
+ TEST_FAIL("%s at %s:%ld, testcase = %lx, vector = %ld",
+ (const char *)uc.args[0], __FILE__,
+ uc.args[1], uc.args[2], uc.args[3]);
+ goto done;
+ case UCALL_DONE:
+ goto done;
+ default:
+ TEST_FAIL("Unknown ucall %lu", uc.cmd);
+ goto done;
+ }
+
+ disabled_quirks = 0;
+ if (testcase & MWAIT_QUIRK_DISABLED)
+ disabled_quirks |= KVM_X86_QUIRK_MWAIT_NEVER_FAULTS;
+ if (testcase & MISC_ENABLES_QUIRK_DISABLED)
+ disabled_quirks |= KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT;
+ vm_enable_cap(vm, KVM_CAP_DISABLE_QUIRKS2, disabled_quirks);
+
+ /*
+ * If the MISC_ENABLES quirk (KVM neglects to update CPUID to
+ * enable/disable MWAIT) is disabled, toggle the ENABLE_MWAIT
+ * bit in MISC_ENABLES accordingly. If the quirk is enabled,
+ * the only valid configuration is MWAIT disabled, as CPUID
+ * can't be manually changed after running the vCPU.
+ */
+ if (!(testcase & MISC_ENABLES_QUIRK_DISABLED)) {
+ TEST_ASSERT(testcase & MWAIT_DISABLED,
+ "Can't toggle CPUID features after running vCPU");
+ continue;
+ }
+
+ vcpu_set_msr(vcpu, MSR_IA32_MISC_ENABLE,
+ (testcase & MWAIT_DISABLED) ? 0 : MSR_IA32_MISC_ENABLE_MWAIT);
+ }
+
+done:
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.36.1.255.ge46751e96f-goog