x86: KVM guest: add basic paravirt support

Add basic KVM paravirt support. Avoid vm-exits on IO delays.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 40cedc2..e5790fe 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -384,6 +384,14 @@
 	  provides the guest with timing infrastructure such as time of day, and
 	  system time
 
+config KVM_GUEST
+	bool "KVM Guest support"
+	select PARAVIRT
+	depends on !(X86_VISWS || X86_VOYAGER)
+	help
+	 This option enables various optimizations for running under the KVM
+	 hypervisor.
+
 source "arch/x86/lguest/Kconfig"
 
 config PARAVIRT