KVM: Move KVM context switch into own function

gcc 4.5 with some special options is able to duplicate the VMX
context switch asm in vmx_vcpu_run(). This results in a compile error
because the inline asm sequence uses an on local label. The non local
label is needed because other code wants to set up the return address.

This patch moves the asm code into an own function and marks
that explicitely noinline to avoid this problem.

Better would be probably to just move it into an .S file.

The diff looks worse than the change really is, it's all just
code movement and no logic change.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/vmx.c

@@ -3890,33 +3890,17 @@ static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
 #define Q "l"
 #endif
 
-static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
+/*
+ * We put this into a separate noinline function to prevent the compiler
+ * from duplicating the code. This is needed because this code
+ * uses non local labels that cannot be duplicated.
+ * Do not put any flow control into this function.
+ * Better would be to put this whole monstrosity into a .S file.
+ */
+static void noinline do_vmx_vcpu_run(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-
-	/* Record the guest's net vcpu time for enforced NMI injections. */
-	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
-		vmx->entry_time = ktime_get();
-
-	/* Don't enter VMX if guest state is invalid, let the exit handler
-	   start emulation until we arrive back to a valid state */
-	if (vmx->emulation_required && emulate_invalid_guest_state)
-		return;
-
-	if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))
-		vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);
-	if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty))
-		vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
-
-	/* When single-stepping over STI and MOV SS, we must clear the
-	 * corresponding interruptibility bits in the guest state. Otherwise
-	 * vmentry fails as it then expects bit 14 (BS) in pending debug
-	 * exceptions being set, but that's not correct for the guest debugging
-	 * case. */
-	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
-		vmx_set_interrupt_shadow(vcpu, 0);
-
-	asm(
+	asm volatile(
 		/* Store host registers */
 		"push %%"R"dx; push %%"R"bp;"
 		"push %%"R"cx \n\t"
@@ -4011,6 +3995,35 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
 #endif
 	      );
+}
+
+static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+	/* Record the guest's net vcpu time for enforced NMI injections. */
+	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
+		vmx->entry_time = ktime_get();
+
+	/* Don't enter VMX if guest state is invalid, let the exit handler
+	   start emulation until we arrive back to a valid state */
+	if (vmx->emulation_required && emulate_invalid_guest_state)
+		return;
+
+	if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))
+		vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);
+	if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty))
+		vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
+
+	/* When single-stepping over STI and MOV SS, we must clear the
+	 * corresponding interruptibility bits in the guest state. Otherwise
+	 * vmentry fails as it then expects bit 14 (BS) in pending debug
+	 * exceptions being set, but that's not correct for the guest debugging
+	 * case. */
+	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
+		vmx_set_interrupt_shadow(vcpu, 0);
+
+	do_vmx_vcpu_run(vcpu);
 
 	vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP)
 				  | (1 << VCPU_EXREG_PDPTR));