KVM: Add coalesced MMIO support (x86 part)

This patch enables coalesced MMIO for x86 architecture.
It defines KVM_MMIO_PAGE_OFFSET and KVM_CAP_COALESCED_MMIO.
It enables the compilation of coalesced_mmio.c.
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/Makefile

@@ -2,7 +2,8 @@
 # Makefile for Kernel-based Virtual Machine module
 #
 
-common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o)
+common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
+                coalesced_mmio.o)
 ifeq ($(CONFIG_KVM_TRACE),y)
 common-objs += $(addprefix ../../../virt/kvm/, kvm_trace.o)
 endif

arch/x86/kvm/x86.c

@@ -885,6 +885,9 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_MP_STATE:
 		r = 1;
 		break;
+	case KVM_CAP_COALESCED_MMIO:
+		r = KVM_COALESCED_MMIO_PAGE_OFFSET;
+		break;
 	case KVM_CAP_VAPIC:
 		r = !kvm_x86_ops->cpu_has_accelerated_tpr();
 		break;

include/asm-x86/kvm_host.h

@@ -27,6 +27,7 @@
 #define KVM_PRIVATE_MEM_SLOTS 4
 
 #define KVM_PIO_PAGE_OFFSET 1
+#define KVM_COALESCED_MMIO_PAGE_OFFSET 2
 
 #define CR3_PAE_RESERVED_BITS ((X86_CR3_PWT | X86_CR3_PCD) - 1)
 #define CR3_NONPAE_RESERVED_BITS ((PAGE_SIZE-1) & ~(X86_CR3_PWT | X86_CR3_PCD))