2 files changed, 75 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 7a5ff646e7e7..4761b768b773 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -116,6 +116,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests
 TEST_GEN_PROGS_x86_64 += x86_64/amx_test
 TEST_GEN_PROGS_x86_64 += x86_64/max_vcpuid_cap_test
 TEST_GEN_PROGS_x86_64 += x86_64/triple_fault_event_test
+TEST_GEN_PROGS_x86_64 += x86_64/recalc_apic_map_test
 TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
 TEST_GEN_PROGS_x86_64 += demand_paging_test
 TEST_GEN_PROGS_x86_64 += dirty_log_test
diff --git a/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c b/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c
new file mode 100644
index 000000000000..4c416ebe7d66
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test edge cases and race conditions in kvm_recalculate_apic_map().
+ */
+
+#include <sys/ioctl.h>
+#include <pthread.h>
+#include <time.h>
+
+#include "processor.h"
+#include "test_util.h"
+#include "kvm_util.h"
+#include "apic.h"
+
+#define TIMEOUT		5	/* seconds */
+
+#define LAPIC_DISABLED	0
+#define LAPIC_X2APIC	(MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE)
+#define MAX_XAPIC_ID	0xff
+
+static void *race(void *arg)
+{
+	struct kvm_lapic_state lapic = {};
+	struct kvm_vcpu *vcpu = arg;
+
+	while (1) {
+		/* Trigger kvm_recalculate_apic_map(). */
+		vcpu_ioctl(vcpu, KVM_SET_LAPIC, &lapic);
+		pthread_testcancel();
+	}
+
+	return NULL;
+}
+
+int main(void)
+{
+	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
+	struct kvm_vcpu *vcpuN;
+	struct kvm_vm *vm;
+	pthread_t thread;
+	time_t t;
+	int i;
+
+	kvm_static_assert(KVM_MAX_VCPUS > MAX_XAPIC_ID);
+
+	/*
+	 * Create the max number of vCPUs supported by selftests so that KVM
+	 * has decent amount of work to do when recalculating the map, i.e. to
+	 * make the problematic window large enough to hit.
+	 */
+	vm = vm_create_with_vcpus(KVM_MAX_VCPUS, NULL, vcpus);
+
+	/*
+	 * Enable x2APIC on all vCPUs so that KVM doesn't bail from the recalc
+	 * due to vCPUs having aliased xAPIC IDs (truncated to 8 bits).
+	 */
+	for (i = 0; i < KVM_MAX_VCPUS; i++)
+		vcpu_set_msr(vcpus[i], MSR_IA32_APICBASE, LAPIC_X2APIC);
+
+	ASSERT_EQ(pthread_create(&thread, NULL, race, vcpus[0]), 0);
+
+	vcpuN = vcpus[KVM_MAX_VCPUS - 1];
+	for (t = time(NULL) + TIMEOUT; time(NULL) < t;) {
+		vcpu_set_msr(vcpuN, MSR_IA32_APICBASE, LAPIC_X2APIC);
+		vcpu_set_msr(vcpuN, MSR_IA32_APICBASE, LAPIC_DISABLED);
+	}
+
+	ASSERT_EQ(pthread_cancel(thread), 0);
+	ASSERT_EQ(pthread_join(thread, NULL), 0);
+
+	kvm_vm_free(vm);
+
+	return 0;
+}