x86: Factor out vmx_handle_cpuid

Shortens vcpu_handle_exit and improves readability.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

hypervisor/arch/x86/vmx.c

@@ -879,6 +879,20 @@ void vcpu_skip_emulated_instruction(unsigned int inst_len)
 	vmcs_write64(GUEST_RIP, vmcs_read64(GUEST_RIP) + inst_len);
 }
 
+static void vmx_handle_cpuid(union registers *guest_regs)
+{
+	/* clear upper 32 bits of the involved registers */
+	guest_regs->rax &= 0xffffffff;
+	guest_regs->rbx &= 0xffffffff;
+	guest_regs->rcx &= 0xffffffff;
+	guest_regs->rdx &= 0xffffffff;
+
+	cpuid((u32 *)&guest_regs->rax, (u32 *)&guest_regs->rbx,
+	      (u32 *)&guest_regs->rcx, (u32 *)&guest_regs->rdx);
+
+	vcpu_skip_emulated_instruction(X86_INST_LEN_CPUID);
+}
+
 static void update_efer(void)
 {
 	unsigned long efer = vmcs_read64(GUEST_IA32_EFER);
@@ -1059,13 +1073,7 @@ void vcpu_handle_exit(struct per_cpu *cpu_data)
 		iommu_check_pending_faults(cpu_data);
 		return;
 	case EXIT_REASON_CPUID:
-		vcpu_skip_emulated_instruction(X86_INST_LEN_CPUID);
-		guest_regs->rax &= 0xffffffff;
-		guest_regs->rbx &= 0xffffffff;
-		guest_regs->rcx &= 0xffffffff;
-		guest_regs->rdx &= 0xffffffff;
-		cpuid((u32 *)&guest_regs->rax, (u32 *)&guest_regs->rbx,
-		      (u32 *)&guest_regs->rcx, (u32 *)&guest_regs->rdx);
+		vmx_handle_cpuid(&cpu_data->guest_regs);
 		return;
 	case EXIT_REASON_VMCALL:
 		vcpu_handle_hypercall();