KVM: x86: extend "struct x86_emulate_ops" with "get_cpuid"

commit bdb42f5a upstream

In order to be able to proceed checks on CPU-specific properties
within the emulator, function "get_cpuid" is introduced.
With "get_cpuid" it is possible to virtually call the guests
"cpuid"-opcode without changing the VM's context.

[mtosatti: cleanup/beautify code]

[bwh: Backport to 2.6.32:
 - Don't use emul_to_vcpu
 - Adjust context]
Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Willy Tarreau <w@1wt.eu>

arch/x86/include/asm/kvm_emulate.h

@@ -109,6 +109,8 @@ struct x86_emulate_ops {
 				unsigned int bytes,
 				struct kvm_vcpu *vcpu);
 
+	bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
+			 u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
 };
 
 /* Type, address-of, and value of an instruction's operand. */

arch/x86/kvm/x86.c

@@ -2871,12 +2871,35 @@ void kvm_report_emulation_failure(struct kvm_vcpu *vcpu, const char *context)
 }
 EXPORT_SYMBOL_GPL(kvm_report_emulation_failure);
 
+static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
+			       u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+{
+	struct kvm_cpuid_entry2 *cpuid = NULL;
+
+	if (eax && ecx)
+		cpuid = kvm_find_cpuid_entry(ctxt->vcpu,
+					    *eax, *ecx);
+
+	if (cpuid) {
+		*eax = cpuid->eax;
+		*ecx = cpuid->ecx;
+		if (ebx)
+			*ebx = cpuid->ebx;
+		if (edx)
+			*edx = cpuid->edx;
+		return true;
+	}
+
+	return false;
+}
+
 static struct x86_emulate_ops emulate_ops = {
 	.read_std            = kvm_read_guest_virt_system,
 	.fetch               = kvm_fetch_guest_virt,
 	.read_emulated       = emulator_read_emulated,
 	.write_emulated      = emulator_write_emulated,
 	.cmpxchg_emulated    = emulator_cmpxchg_emulated,
+	.get_cpuid           = emulator_get_cpuid,
 };
 
 static void cache_all_regs(struct kvm_vcpu *vcpu)