Or rather just implement one different function as opposed
to the native one : the read function.

We synthesize the values.

Acked-by:  Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/Makefile    |    2 +-
 arch/x86/xen/apic.c      |   17 +++++++++++++++++
 arch/x86/xen/enlighten.c |    2 ++
 arch/x86/xen/xen-ops.h   |    4 ++++
 4 files changed, 24 insertions(+), 1 deletions(-)
 create mode 100644 arch/x86/xen/apic.c

diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index add2c2d..96ab2c0 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -20,5 +20,5 @@ obj-$(CONFIG_EVENT_TRACING) += trace.o
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
 obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
-obj-$(CONFIG_XEN_DOM0)		+= vga.o
+obj-$(CONFIG_XEN_DOM0)		+= apic.o vga.o
 obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
new file mode 100644
index 0000000..71ed91c
--- /dev/null
+++ b/arch/x86/xen/apic.c
@@ -0,0 +1,17 @@
+#include <linux/init.h>
+#include <asm/x86_init.h>
+
+unsigned int xen_io_apic_read(unsigned apic, unsigned reg)
+{
+	if (reg == 0x1)
+		return 0x00170020;
+	else if (reg == 0x0)
+		return apic << 24;
+
+	return 0xff;
+}
+
+void __init xen_init_apic(void)
+{
+	x86_ioapic.read = xen_io_apic_read;
+}
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 0732326..93a03195 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1377,6 +1377,8 @@ asmlinkage void __init xen_start_kernel(void)
 		xen_start_info->console.domU.mfn = 0;
 		xen_start_info->console.domU.evtchn = 0;
 
+		xen_init_apic();
+
 		/* Make sure ACS will be enabled */
 		pci_request_acs();
 
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index b095739..45c0c06 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -92,11 +92,15 @@ struct dom0_vga_console_info;
 
 #ifdef CONFIG_XEN_DOM0
 void __init xen_init_vga(const struct dom0_vga_console_info *, size_t size);
+void __init xen_init_apic(void);
 #else
 static inline void __init xen_init_vga(const struct dom0_vga_console_info *info,
 				       size_t size)
 {
 }
+static inline void __init xen_init_apic(void)
+{
+}
 #endif
 
 /* Declare an asm function, along with symbols needed to make it
-- 
1.7.7.5