1 files changed, 43 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/lib/x86_64/apic.c b/tools/testing/selftests/kvm/lib/x86_64/apic.c
new file mode 100644
index 000000000000..89153a333e83
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86_64/apic.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021, Google LLC.
+ */
+
+#include "apic.h"
+
+void apic_disable(void)
+{
+	wrmsr(MSR_IA32_APICBASE,
+	      rdmsr(MSR_IA32_APICBASE) &
+		~(MSR_IA32_APICBASE_ENABLE | MSR_IA32_APICBASE_EXTD));
+}
+
+void xapic_enable(void)
+{
+	uint64_t val = rdmsr(MSR_IA32_APICBASE);
+
+	/* Per SDM: to enable xAPIC when in x2APIC must first disable APIC */
+	if (val & MSR_IA32_APICBASE_EXTD) {
+		apic_disable();
+		wrmsr(MSR_IA32_APICBASE,
+		      rdmsr(MSR_IA32_APICBASE) | MSR_IA32_APICBASE_ENABLE);
+	} else if (!(val & MSR_IA32_APICBASE_ENABLE)) {
+		wrmsr(MSR_IA32_APICBASE, val | MSR_IA32_APICBASE_ENABLE);
+	}
+
+	/*
+	 * Per SDM: reset value of spurious interrupt vector register has the
+	 * APIC software enabled bit=0. It must be enabled in addition to the
+	 * enable bit in the MSR.
+	 */
+	val = xapic_read_reg(APIC_SPIV) | APIC_SPIV_APIC_ENABLED;
+	xapic_write_reg(APIC_SPIV, val);
+}
+
+void x2apic_enable(void)
+{
+	wrmsr(MSR_IA32_APICBASE, rdmsr(MSR_IA32_APICBASE) |
+	      MSR_IA32_APICBASE_ENABLE | MSR_IA32_APICBASE_EXTD);
+	x2apic_write_reg(APIC_SPIV,
+			 x2apic_read_reg(APIC_SPIV) | APIC_SPIV_APIC_ENABLED);
+}