KVM: x86: Add return value to kvm_cpuid().

Return false in kvm_cpuid() when it fails to find the cpuid
entry. Also, this routine(and its caller) is optimized with
a new argument - check_limit, so that the check_cpuid_limit()
fall back can be avoided.
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -219,8 +219,8 @@ struct x86_emulate_ops {
 			 struct x86_instruction_info *info,
 			 enum x86_intercept_stage stage);
 
-	void (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
-			  u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
+	bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt, u32 *eax, u32 *ebx,
+			  u32 *ecx, u32 *edx, bool check_limit);
 	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
 
 	unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);

arch/x86/kvm/cpuid.c

@@ -853,16 +853,24 @@ static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
 	return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
 }
 
-void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
+	       u32 *ecx, u32 *edx, bool check_limit)
 {
 	u32 function = *eax, index = *ecx;
 	struct kvm_cpuid_entry2 *best;
+	bool entry_found = true;
 
 	best = kvm_find_cpuid_entry(vcpu, function, index);
 
-	if (!best)
+	if (!best) {
+		entry_found = false;
+		if (!check_limit)
+			goto out;
+
 		best = check_cpuid_limit(vcpu, function, index);
+	}
 
+out:
 	if (best) {
 		*eax = best->eax;
 		*ebx = best->ebx;
@@ -870,7 +878,8 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
 		*edx = best->edx;
 	} else
 		*eax = *ebx = *ecx = *edx = 0;
-	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx);
+	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found);
+	return entry_found;
 }
 EXPORT_SYMBOL_GPL(kvm_cpuid);
 
@@ -883,7 +892,7 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
 
 	eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
 	ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
-	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
+	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true);
 	kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
 	kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
 	kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);

arch/x86/kvm/cpuid.h

@@ -21,7 +21,8 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
 			      struct kvm_cpuid2 *cpuid,
 			      struct kvm_cpuid_entry2 __user *entries);
-void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
+bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
+	       u32 *ecx, u32 *edx, bool check_limit);
 
 int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);
 

arch/x86/kvm/emulate.c

@@ -2333,7 +2333,7 @@ static int emulator_has_longmode(struct x86_emulate_ctxt *ctxt)
 
 	eax = 0x80000001;
 	ecx = 0;
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
 	return edx & bit(X86_FEATURE_LM);
 }
 
@@ -2636,7 +2636,7 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt)
 	u32 eax, ebx, ecx, edx;
 
 	eax = ecx = 0;
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
 	return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx
 		&& ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx
 		&& edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
@@ -2656,7 +2656,7 @@ static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)
 
 	eax = 0x00000000;
 	ecx = 0x00000000;
-	ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
 	/*
 	 * Intel ("GenuineIntel")
 	 * remark: Intel CPUs only support "syscall" in 64bit
@@ -3551,7 +3551,7 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
 	/*
 	 * Check MOVBE is set in the guest-visible CPUID leaf.
 	 */
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
 	if (!(ecx & FFL(MOVBE)))
 		return emulate_ud(ctxt);
 
@@ -3865,7 +3865,7 @@ static int em_cpuid(struct x86_emulate_ctxt *ctxt)
 
 	eax = reg_read(ctxt, VCPU_REGS_RAX);
 	ecx = reg_read(ctxt, VCPU_REGS_RCX);
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, true);
 	*reg_write(ctxt, VCPU_REGS_RAX) = eax;
 	*reg_write(ctxt, VCPU_REGS_RBX) = ebx;
 	*reg_write(ctxt, VCPU_REGS_RCX) = ecx;
@@ -3924,7 +3924,7 @@ static int check_fxsr(struct x86_emulate_ctxt *ctxt)
 {
 	u32 eax = 1, ebx, ecx = 0, edx;
 
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
 	if (!(edx & FFL(FXSR)))
 		return emulate_ud(ctxt);
 

arch/x86/kvm/svm.c

@@ -1593,7 +1593,7 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	}
 	init_vmcb(svm);
 
-	kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
+	kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, true);
 	kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
 
 	if (kvm_vcpu_apicv_active(vcpu) && !init_event)

arch/x86/kvm/trace.h

@@ -151,8 +151,8 @@ TRACE_EVENT(kvm_fast_mmio,
  */
 TRACE_EVENT(kvm_cpuid,
 	TP_PROTO(unsigned int function, unsigned long rax, unsigned long rbx,
-		 unsigned long rcx, unsigned long rdx),
-	TP_ARGS(function, rax, rbx, rcx, rdx),
+		 unsigned long rcx, unsigned long rdx, bool found),
+	TP_ARGS(function, rax, rbx, rcx, rdx, found),
 
 	TP_STRUCT__entry(
 		__field(	unsigned int,	function	)
@@ -160,6 +160,7 @@ TRACE_EVENT(kvm_cpuid,
 		__field(	unsigned long,	rbx		)
 		__field(	unsigned long,	rcx		)
 		__field(	unsigned long,	rdx		)
+		__field(	bool,		found		)
 	),
 
 	TP_fast_assign(
@@ -168,11 +169,13 @@ TRACE_EVENT(kvm_cpuid,
 		__entry->rbx		= rbx;
 		__entry->rcx		= rcx;
 		__entry->rdx		= rdx;
+		__entry->found		= found;
 	),
 
-	TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx",
+	TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx, cpuid entry %s",
 		  __entry->function, __entry->rax,
-		  __entry->rbx, __entry->rcx, __entry->rdx)
+		  __entry->rbx, __entry->rcx, __entry->rdx,
+		  __entry->found ? "found" : "not found")
 );
 
 #define AREG(x) { APIC_##x, "APIC_" #x }

arch/x86/kvm/x86.c

@@ -5206,10 +5206,10 @@ static int emulator_intercept(struct x86_emulate_ctxt *ctxt,
 	return kvm_x86_ops->check_intercept(emul_to_vcpu(ctxt), info, stage);
 }
 
-static void emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
-			       u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
+			u32 *eax, u32 *ebx, u32 *ecx, u32 *edx, bool check_limit)
 {
-	kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx);
+	return kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx, check_limit);
 }
 
 static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)