[kvm-unit-tests PATCH 1/2] nVMX: Remove the IA32_DEBUGCTLMSR access in debugctls test

[Chenyi Qiang <chenyi.qiang@intel.com>]

Current debug controls test can pass but will trigger some error
messages because it tries to access LBR (bit 0) and BTF (bit 1) in
IA32_DEBUGCTLMSR:

  kvm_intel: kvm [18663]: vcpu0, guest rIP: 0x407de7 Unhandled WRMSR(0x1d9) = 0x1
  kvm_intel: kvm [18663]: vcpu0, guest rIP: 0x0 Unhandled WRMSR(0x1d9) = 0x2
  kvm_intel: kvm [18663]: vcpu0, guest rIP: 0x40936f Unhandled WRMSR(0x1d9) = 0x3
  kvm_intel: kvm [18663]: vcpu0, guest rIP: 0x40cf09 Unhandled WRMSR(0x1d9) = 0x1
  kvm_intel: kvm [18663]: vcpu0, guest rIP: 0x40940d Unhandled WRMSR(0x1d9) = 0x3

The IA32_DEBUGCTLMSR value isn't used as a criterion for determining
whether the test is passed. It only provides some hints on the expected
values with the control of {ENT_LOAD, EXIT_SAVE}_DBGCTLS. The reality is
different because KVM only allows the guest to access the valid bits
depending on the supported features. Luckily, KVM will exempt BTF and
LBR from validity check which makes the test survive.

Considering that IA32_DEBUGCTLMSR access is not practically effective
and will bring error messages, eliminate the related code and rename
the test to specifically address the DR7 check.

Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
---
 x86/vmx_tests.c | 46 ++++++++++++++--------------------------------
 1 file changed, 14 insertions(+), 32 deletions(-)

diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 0b3cfe50..1832bda3 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -1850,21 +1850,18 @@ static int nmi_hlt_exit_handler(union exit_reason exit_reason)
 }
 
 
-static int dbgctls_init(struct vmcs *vmcs)
+static int dbgctls_dr7_init(struct vmcs *vmcs)
 {
 	u64 dr7 = 0x402;
 	u64 zero = 0;
 
-	msr_bmp_init();
 	asm volatile(
 		"mov %0,%%dr0\n\t"
 		"mov %0,%%dr1\n\t"
 		"mov %0,%%dr2\n\t"
 		"mov %1,%%dr7\n\t"
 		: : "r" (zero), "r" (dr7));
-	wrmsr(MSR_IA32_DEBUGCTLMSR, 0x1);
 	vmcs_write(GUEST_DR7, 0x404);
-	vmcs_write(GUEST_DEBUGCTL, 0x2);
 
 	vmcs_write(ENT_CONTROLS, vmcs_read(ENT_CONTROLS) | ENT_LOAD_DBGCTLS);
 	vmcs_write(EXI_CONTROLS, vmcs_read(EXI_CONTROLS) | EXI_SAVE_DBGCTLS);
@@ -1872,23 +1869,19 @@ static int dbgctls_init(struct vmcs *vmcs)
 	return VMX_TEST_START;
 }
 
-static void dbgctls_main(void)
+static void dbgctls_dr7_main(void)
 {
-	u64 dr7, debugctl;
+	u64 dr7;
 
 	asm volatile("mov %%dr7,%0" : "=r" (dr7));
-	debugctl = rdmsr(MSR_IA32_DEBUGCTLMSR);
-	/* Commented out: KVM does not support DEBUGCTL so far */
-	(void)debugctl;
-	report(dr7 == 0x404, "Load debug controls" /* && debugctl == 0x2 */);
+	report(dr7 == 0x404, "DR7: Load debug controls");
 
 	dr7 = 0x408;
 	asm volatile("mov %0,%%dr7" : : "r" (dr7));
-	wrmsr(MSR_IA32_DEBUGCTLMSR, 0x3);
 
 	vmx_set_test_stage(0);
 	vmcall();
-	report(vmx_get_test_stage() == 1, "Save debug controls");
+	report(vmx_get_test_stage() == 1, "DR7: Save debug controls");
 
 	if (ctrl_enter_rev.set & ENT_LOAD_DBGCTLS ||
 	    ctrl_exit_rev.set & EXI_SAVE_DBGCTLS) {
@@ -1899,46 +1892,37 @@ static void dbgctls_main(void)
 	vmcall();
 
 	asm volatile("mov %%dr7,%0" : "=r" (dr7));
-	debugctl = rdmsr(MSR_IA32_DEBUGCTLMSR);
-	/* Commented out: KVM does not support DEBUGCTL so far */
-	(void)debugctl;
 	report(dr7 == 0x402,
-	       "Guest=host debug controls" /* && debugctl == 0x1 */);
+	       "DR7: Guest=host debug controls");
 
 	dr7 = 0x408;
 	asm volatile("mov %0,%%dr7" : : "r" (dr7));
-	wrmsr(MSR_IA32_DEBUGCTLMSR, 0x3);
 
 	vmx_set_test_stage(3);
 	vmcall();
-	report(vmx_get_test_stage() == 4, "Don't save debug controls");
+	report(vmx_get_test_stage() == 4, "DR7: Don't save debug controls");
 }
 
-static int dbgctls_exit_handler(union exit_reason exit_reason)
+static int dbgctls_dr7_exit_handler(union exit_reason exit_reason)
 {
 	u32 insn_len = vmcs_read(EXI_INST_LEN);
 	u64 guest_rip = vmcs_read(GUEST_RIP);
-	u64 dr7, debugctl;
+	u64 dr7;
 
 	asm volatile("mov %%dr7,%0" : "=r" (dr7));
-	debugctl = rdmsr(MSR_IA32_DEBUGCTLMSR);
 
 	switch (exit_reason.basic) {
 	case VMX_VMCALL:
 		switch (vmx_get_test_stage()) {
 		case 0:
-			if (dr7 == 0x400 && debugctl == 0 &&
-			    vmcs_read(GUEST_DR7) == 0x408 /* &&
-			    Commented out: KVM does not support DEBUGCTL so far
-			    vmcs_read(GUEST_DEBUGCTL) == 0x3 */)
+			if (dr7 == 0x400 &&
+			    vmcs_read(GUEST_DR7) == 0x408)
 				vmx_inc_test_stage();
 			break;
 		case 2:
 			dr7 = 0x402;
 			asm volatile("mov %0,%%dr7" : : "r" (dr7));
-			wrmsr(MSR_IA32_DEBUGCTLMSR, 0x1);
 			vmcs_write(GUEST_DR7, 0x404);
-			vmcs_write(GUEST_DEBUGCTL, 0x2);
 
 			vmcs_write(ENT_CONTROLS,
 				vmcs_read(ENT_CONTROLS) & ~ENT_LOAD_DBGCTLS);
@@ -1946,10 +1930,8 @@ static int dbgctls_exit_handler(union exit_reason exit_reason)
 				vmcs_read(EXI_CONTROLS) & ~EXI_SAVE_DBGCTLS);
 			break;
 		case 3:
-			if (dr7 == 0x400 && debugctl == 0 &&
-			    vmcs_read(GUEST_DR7) == 0x404 /* &&
-			    Commented out: KVM does not support DEBUGCTL so far
-			    vmcs_read(GUEST_DEBUGCTL) == 0x2 */)
+			if (dr7 == 0x400 &&
+			    vmcs_read(GUEST_DR7) == 0x404)
 				vmx_inc_test_stage();
 			break;
 		}
@@ -11402,7 +11384,7 @@ struct vmx_test vmx_tests[] = {
 		interrupt_exit_handler, NULL, {0} },
 	{ "nmi_hlt", nmi_hlt_init, nmi_hlt_main,
 		nmi_hlt_exit_handler, NULL, {0} },
-	{ "debug controls", dbgctls_init, dbgctls_main, dbgctls_exit_handler,
+	{ "debug controls dr7", dbgctls_dr7_init, dbgctls_dr7_main, dbgctls_dr7_exit_handler,
 		NULL, {0} },
 	{ "MSR switch", msr_switch_init, msr_switch_main,
 		msr_switch_exit_handler, NULL, {0}, msr_switch_entry_failure },
-- 
2.43.5