kvm/x86: add support for MONITOR_TRAP_FLAG

Allow a nested hypervisor to single step its guests.
Signed-off-by: Mihai Donțu <mihai.dontu@gmail.com>
[Fix overlong line. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/vmx.h

@@ -47,6 +47,7 @@
 #define CPU_BASED_MOV_DR_EXITING                0x00800000
 #define CPU_BASED_UNCOND_IO_EXITING             0x01000000
 #define CPU_BASED_USE_IO_BITMAPS                0x02000000
+#define CPU_BASED_MONITOR_TRAP_FLAG             0x08000000
 #define CPU_BASED_USE_MSR_BITMAPS               0x10000000
 #define CPU_BASED_MONITOR_EXITING               0x20000000
 #define CPU_BASED_PAUSE_EXITING                 0x40000000

arch/x86/include/uapi/asm/vmx.h

@@ -58,6 +58,7 @@
 #define EXIT_REASON_INVALID_STATE       33
 #define EXIT_REASON_MSR_LOAD_FAIL       34
 #define EXIT_REASON_MWAIT_INSTRUCTION   36
+#define EXIT_REASON_MONITOR_TRAP_FLAG   37
 #define EXIT_REASON_MONITOR_INSTRUCTION 39
 #define EXIT_REASON_PAUSE_INSTRUCTION   40
 #define EXIT_REASON_MCE_DURING_VMENTRY  41
@@ -106,6 +107,7 @@
 	{ EXIT_REASON_MSR_READ,              "MSR_READ" }, \
 	{ EXIT_REASON_MSR_WRITE,             "MSR_WRITE" }, \
 	{ EXIT_REASON_MWAIT_INSTRUCTION,     "MWAIT_INSTRUCTION" }, \
+	{ EXIT_REASON_MONITOR_TRAP_FLAG,     "MONITOR_TRAP_FLAG" }, \
 	{ EXIT_REASON_MONITOR_INSTRUCTION,   "MONITOR_INSTRUCTION" }, \
 	{ EXIT_REASON_PAUSE_INSTRUCTION,     "PAUSE_INSTRUCTION" }, \
 	{ EXIT_REASON_MCE_DURING_VMENTRY,    "MCE_DURING_VMENTRY" }, \

arch/x86/kvm/vmx.c

@@ -2443,10 +2443,10 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 		CPU_BASED_CR8_LOAD_EXITING | CPU_BASED_CR8_STORE_EXITING |
 #endif
 		CPU_BASED_MOV_DR_EXITING | CPU_BASED_UNCOND_IO_EXITING |
-		CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_EXITING |
-		CPU_BASED_RDPMC_EXITING | CPU_BASED_RDTSC_EXITING |
-		CPU_BASED_PAUSE_EXITING | CPU_BASED_TPR_SHADOW |
-		CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
+		CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_TRAP_FLAG |
+		CPU_BASED_MONITOR_EXITING | CPU_BASED_RDPMC_EXITING |
+		CPU_BASED_RDTSC_EXITING | CPU_BASED_PAUSE_EXITING |
+		CPU_BASED_TPR_SHADOW | CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
 	/*
 	 * We can allow some features even when not supported by the
 	 * hardware. For example, L1 can specify an MSR bitmap - and we
@@ -6246,6 +6246,11 @@ static int handle_mwait(struct kvm_vcpu *vcpu)
 	return handle_nop(vcpu);
 }
 
+static int handle_monitor_trap(struct kvm_vcpu *vcpu)
+{
+	return 1;
+}
+
 static int handle_monitor(struct kvm_vcpu *vcpu)
 {
 	printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
@@ -7327,6 +7332,7 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 	[EXIT_REASON_EPT_MISCONFIG]           = handle_ept_misconfig,
 	[EXIT_REASON_PAUSE_INSTRUCTION]       = handle_pause,
 	[EXIT_REASON_MWAIT_INSTRUCTION]	      = handle_mwait,
+	[EXIT_REASON_MONITOR_TRAP_FLAG]       = handle_monitor_trap,
 	[EXIT_REASON_MONITOR_INSTRUCTION]     = handle_monitor,
 	[EXIT_REASON_INVEPT]                  = handle_invept,
 	[EXIT_REASON_INVVPID]                 = handle_invvpid,
@@ -7587,6 +7593,8 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
 		return true;
 	case EXIT_REASON_MWAIT_INSTRUCTION:
 		return nested_cpu_has(vmcs12, CPU_BASED_MWAIT_EXITING);
+	case EXIT_REASON_MONITOR_TRAP_FLAG:
+		return nested_cpu_has(vmcs12, CPU_BASED_MONITOR_TRAP_FLAG);
 	case EXIT_REASON_MONITOR_INSTRUCTION:
 		return nested_cpu_has(vmcs12, CPU_BASED_MONITOR_EXITING);
 	case EXIT_REASON_PAUSE_INSTRUCTION: