Add tests to verify that the EFER MSR is correctly handled during VM-Exit.

The following behaviors are verified:

  1. The EFER MSR is saved to VMCS during VM-Exit iff the "Save EFER"
     VM-Exit control is set.

  2. The EFER MSR is not saved to VMCS during VM-Exit iff the "Save EFER"
     VM-Exit control is cleared.

  3. The EFER MSR is loaded with the value from VMCS host EFER MSR field
     iff the "Load EFER" VM-Exit control is set.

  4. The EFER MSR is retained iff the "Load EFER" VM-Exit control is
     cleared.

Signed-off-by: Xin Li <xin@zytor.com>
---
 x86/vmx_tests.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 2b6814ef..daa1504c 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -12195,6 +12195,131 @@ static void vmx_exit_control_fred_test(void)
 	test_set_guest_finished();
 }
 
+#define GUEST_INIT_EFER	(EFER_SCE | EFER_LME | EFER_LMA)
+#define GUEST_SET_EFER	(EFER_LME | EFER_LMA | EFER_NX)
+
+static void vmx_exit_control_efer_test_guest(void)
+{
+	wrmsr(MSR_EFER, GUEST_SET_EFER);
+
+	vmcall();
+}
+
+static void vmx_exit_control_efer_test(void)
+{
+	bool entry_not_load_efer_tested = false;
+	u64 host_efer = rdmsr(MSR_EFER);
+
+	if (!(ctrl_exit_rev.clr & EXI_SAVE_EFER)) {
+		report_skip("Save EFER exit control is not available");
+		return;
+	}
+
+	if (!(ctrl_exit_rev.clr & EXI_LOAD_EFER)) {
+		report_skip("Load EFER exit control is not available");
+		return;
+	}
+
+	if (!(ctrl_enter_rev.clr & ENT_LOAD_EFER)) {
+		report_skip("Load EFER entry control is not available");
+		return;
+	}
+
+	/* Allow the guest to read the EFER MSR directly */
+	msr_bmp_init();
+
+	vmcs_set_bits(ENT_CONTROLS, ENT_LOAD_EFER);
+	vmcs_write(HOST_EFER, host_efer);
+
+test_again:
+	/*
+	 * Case 1:
+	 *
+	 * The EFER MSR is not saved to VMCS during VM-Exit if the "Save EFER"
+	 * VM-Exit control is cleared.
+	 *
+	 * The EFER MSR is retained if the "Load EFER" VM-Exit control is
+	 * cleared.
+	 */
+	vmcs_clear_bits(EXI_CONTROLS, EXI_SAVE_EFER | EXI_LOAD_EFER);
+	if (entry_not_load_efer_tested)
+		test_override_guest(vmx_exit_control_efer_test_guest);
+	else
+		test_set_guest(vmx_exit_control_efer_test_guest);
+	vmcs_write(GUEST_EFER, GUEST_INIT_EFER);
+
+	enter_guest();
+	report(rdmsr(MSR_EFER) == GUEST_SET_EFER, "The EFER MSR is retained at VM Exit");
+	report(vmcs_read(GUEST_EFER) == GUEST_INIT_EFER, "VMCS guest EFER is not saved at VM Exit");
+
+	wrmsr(MSR_EFER, host_efer);
+
+	/*
+	 * Case 2:
+	 *
+	 * The EFER MSR is not saved to VMCS during VM-Exit if the "Save EFER"
+	 * VM-Exit control is cleared.
+	 *
+	 * The EFER MSR is loaded with the value from VMCS host EFER MSR field
+	 * if the "Load EFER" VM-Exit control is set.
+	 */
+	vmcs_clear_bits(EXI_CONTROLS, EXI_SAVE_EFER);
+	vmcs_set_bits(EXI_CONTROLS, EXI_LOAD_EFER);
+	test_override_guest(vmx_exit_control_efer_test_guest);
+	vmcs_write(GUEST_EFER, GUEST_INIT_EFER);
+
+	enter_guest();
+	report(rdmsr(MSR_EFER) == host_efer, "VMCS host EFER is loaded at VM Exit");
+	report(vmcs_read(GUEST_EFER) == GUEST_INIT_EFER, "VMCS guest EFER is not saved at VM Exit");
+
+	/*
+	 * Case 3:
+	 *
+	 * The EFER MSR is saved to VMCS during VM-Exit if the "Save EFER"
+	 * VM-Exit control is set.
+	 *
+	 * The EFER MSR is retained if the "Load EFER" VM-Exit control is
+	 * cleared.
+	 */
+	vmcs_set_bits(EXI_CONTROLS, EXI_SAVE_EFER);
+	vmcs_clear_bits(EXI_CONTROLS, EXI_LOAD_EFER);
+	test_override_guest(vmx_exit_control_efer_test_guest);
+	vmcs_write(GUEST_EFER, GUEST_INIT_EFER);
+
+	enter_guest();
+	report(rdmsr(MSR_EFER) == GUEST_SET_EFER, "The EFER MSR is retained at VM Exit");
+	report(vmcs_read(GUEST_EFER) == GUEST_SET_EFER, "VMCS guest EFER is saved at VM Exit");
+
+	wrmsr(MSR_EFER, host_efer);
+
+	/*
+	 * Case 4:
+	 *
+	 * The EFER MSR is saved to VMCS during VM-Exit if the "Save EFER"
+	 * VM-Exit control is set.
+	 *
+	 * The EFER MSR is loaded with the value from VMCS host EFER MSR field
+	 * if the "Load EFER" VM-Exit control is set.
+	 */
+	vmcs_set_bits(EXI_CONTROLS, EXI_SAVE_EFER | EXI_LOAD_EFER);
+	test_override_guest(vmx_exit_control_efer_test_guest);
+	vmcs_write(GUEST_EFER, GUEST_INIT_EFER);
+
+	enter_guest();
+	report(rdmsr(MSR_EFER) == host_efer, "VMCS host EFER is loaded at VM Exit");
+	report(vmcs_read(GUEST_EFER) == GUEST_SET_EFER, "VMCS guest EFER is saved at VM Exit");
+
+	if (!entry_not_load_efer_tested) {
+		entry_not_load_efer_tested = true;
+
+		/* Clear ENT_LOAD_EFER and run tests again */
+		vmcs_clear_bits(ENT_CONTROLS, ENT_LOAD_EFER);
+		goto test_again;
+	}
+
+	test_set_guest_finished();
+}
+
 #define TEST(name) { #name, .v2 = name }
 
 /* name/init/guest_main/exit_handler/vmfail_handler */
@@ -12314,5 +12439,6 @@ struct vmx_test vmx_tests[] = {
 	/* "Load CET" VM-entry/exit controls tests. */
 	TEST(vmx_cet_test),
 	TEST(vmx_exit_control_fred_test),
+	TEST(vmx_exit_control_efer_test),
 	{ NULL, NULL, NULL, NULL },
 };
-- 
2.54.0