diff -r 64a932c92a7c xen/arch/x86/msi.c
--- a/xen/arch/x86/msi.c	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/arch/x86/msi.c	Wed Jun 17 18:38:34 2009 +0200
@@ -192,7 +192,7 @@ static void read_msi_msg(struct msi_desc
     }
 
     if ( iommu_enabled )
-        msi_msg_read_remap_rte(entry, msg);
+        iommu_read_msi_from_ire(entry, msg);
 }
 
 static int set_vector_msi(struct msi_desc *entry)
diff -r 64a932c92a7c xen/drivers/passthrough/amd/iommu_intr.c
--- a/xen/drivers/passthrough/amd/iommu_intr.c	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/drivers/passthrough/amd/iommu_intr.c	Wed Jun 17 18:38:34 2009 +0200
@@ -231,6 +231,18 @@ void amd_iommu_msi_msg_update_ire(
     update_intremap_entry_from_msi_msg(iommu, pdev, msg);
 }
 
+unsigned int amd_iommu_read_ioapic_from_ire(
+    unsigned int apic, unsigned int reg)
+{
+    *IO_APIC_BASE(apic) = reg;
+    return *(IO_APIC_BASE(apic)+4);
+}
+
+void amd_iommu_read_msi_from_ire(
+    struct msi_desc *msi_desc, struct msi_msg *msg)
+{
+}
+
 int __init deallocate_intremap_table(void)
 {
     if ( int_remap_table )
diff -r 64a932c92a7c xen/drivers/passthrough/amd/pci_amd_iommu.c
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c	Wed Jun 17 18:38:34 2009 +0200
@@ -439,4 +439,6 @@ struct iommu_ops amd_iommu_ops = {
     .get_device_group_id = amd_iommu_group_id,
     .update_ire_from_apic = amd_iommu_ioapic_update_ire,
     .update_ire_from_msi = amd_iommu_msi_msg_update_ire,
+    .read_apic_from_ire = amd_iommu_read_ioapic_from_ire,
+    .read_msi_from_ire = amd_iommu_read_msi_from_ire,
 };
diff -r 64a932c92a7c xen/drivers/passthrough/iommu.c
--- a/xen/drivers/passthrough/iommu.c	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/drivers/passthrough/iommu.c	Wed Jun 17 18:38:34 2009 +0200
@@ -263,14 +263,10 @@ static int iommu_setup(void)
 {
     int rc = -ENODEV;
 
-    if ( !iommu_enabled )
-        goto out;
-
     rc = iommu_hardware_setup();
 
     iommu_enabled = (rc == 0);
 
- out:
     if ( force_iommu && !iommu_enabled )
         panic("IOMMU setup failed, crash Xen for security purpose!\n");
 
@@ -336,6 +332,20 @@ void iommu_update_ire_from_msi(
     struct iommu_ops *ops = iommu_get_ops();
     ops->update_ire_from_msi(msi_desc, msg);
 }
+
+void iommu_read_msi_from_ire(
+    struct msi_desc *msi_desc, struct msi_msg *msg)
+{
+    struct iommu_ops *ops = iommu_get_ops();
+    ops->read_msi_from_ire(msi_desc, msg);
+}
+
+unsigned int iommu_read_apic_from_ire(unsigned int apic, unsigned int reg)
+{
+    struct iommu_ops *ops = iommu_get_ops();
+    return ops->read_apic_from_ire(apic, reg);
+}
+
 /*
  * Local variables:
  * mode: C
diff -r 64a932c92a7c xen/drivers/passthrough/vtd/iommu.c
--- a/xen/drivers/passthrough/vtd/iommu.c	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/drivers/passthrough/vtd/iommu.c	Wed Jun 17 18:38:34 2009 +0200
@@ -1989,6 +1989,8 @@ struct iommu_ops intel_iommu_ops = {
     .get_device_group_id = intel_iommu_group_id,
     .update_ire_from_apic = io_apic_write_remap_rte,
     .update_ire_from_msi = msi_msg_write_remap_rte,
+    .read_apic_from_ire = io_apic_read_remap_rte,
+    .read_msi_from_ire = msi_msg_read_remap_rte,
 };
 
 /*
diff -r 64a932c92a7c xen/include/asm-x86/hvm/svm/amd-iommu-proto.h
--- a/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h	Wed Jun 17 18:38:34 2009 +0200
@@ -87,6 +87,10 @@ void amd_iommu_ioapic_update_ire(
     unsigned int apic, unsigned int reg, unsigned int value);
 void amd_iommu_msi_msg_update_ire(
     struct msi_desc *msi_desc, struct msi_msg *msg);
+void amd_iommu_read_msi_from_ire(
+    struct msi_desc *msi_desc, struct msi_msg *msg);
+unsigned int amd_iommu_read_ioapic_from_ire(
+    unsigned int apic, unsigned int reg);
 
 static inline u32 get_field_from_reg_u32(u32 reg_value, u32 mask, u32 shift)
 {
diff -r 64a932c92a7c xen/include/asm-x86/io_apic.h
--- a/xen/include/asm-x86/io_apic.h	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/include/asm-x86/io_apic.h	Wed Jun 17 18:38:34 2009 +0200
@@ -131,7 +131,7 @@ static inline unsigned int io_apic_read(
 static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 {
 	if (ioapic_reg_remapped(reg))
-		return io_apic_read_remap_rte(apic, reg);
+		return iommu_read_apic_from_ire(apic, reg);
 	*IO_APIC_BASE(apic) = reg;
 	return *(IO_APIC_BASE(apic)+4);
 }
diff -r 64a932c92a7c xen/include/xen/iommu.h
--- a/xen/include/xen/iommu.h	Tue Jun 16 14:19:34 2009 +0100
+++ b/xen/include/xen/iommu.h	Wed Jun 17 18:38:34 2009 +0200
@@ -107,10 +107,14 @@ struct iommu_ops {
     int (*get_device_group_id)(u8 bus, u8 devfn);
     void (*update_ire_from_apic)(unsigned int apic, unsigned int reg, unsigned int value);
     void (*update_ire_from_msi)(struct msi_desc *msi_desc, struct msi_msg *msg);
+    void (*read_msi_from_ire)(struct msi_desc *msi_desc, struct msi_msg *msg);
+    unsigned int (*read_apic_from_ire)(unsigned int apic, unsigned int reg);
 };
 
 void iommu_update_ire_from_apic(unsigned int apic, unsigned int reg, unsigned int value);
 void iommu_update_ire_from_msi(struct msi_desc *msi_desc, struct msi_msg *msg);
+void iommu_read_msi_from_ire(struct msi_desc *msi_desc, struct msi_msg *msg);
+unsigned int iommu_read_apic_from_ire(unsigned int apic, unsigned int reg);
 
 void iommu_suspend(void);
 void iommu_resume(void);