by the vmm 140 as the guest memory 152 a part of the memory group b 115 b is allocated by the vmm 140 and the guest os can handle the guest memory 152 as if the guest memory 152 were a physical memory on the virtual machine 150 the virtualized pci device 153 is a virtual device that behaves like the hba 119 implemented by software based on pci specifications and includes a pci configuration space 154 based on the pci specifications disclosed in pci local bus specification revision 3 0 issued by pci sig aug 12 2002 and a message signal interrupt x msi x area 155 the msi x area 155 retains a guest vector number 156 for notifying of an interrupt vector and a virtualized cpu local advanced programmable interrupt controller lapic id 157 and may include other data based on the msi x specifications as necessary further the data retained by the virtualized pci device 153 is extracted onto the guest memory 152 and a data update is trapped by the vmm 140 this embodiment is directed to an example where the hba 119 is set as the virtualized pci device 153 because the storage device 120 is set as a target but this invention can be applied to the virtualized pci device of another kind such as the nic 118 the file server os 160 is an operating system that operates on the virtual machine 150 includes a driver 161 for a virtualized pci device and controls the virtualized pci device 153 by using the driver 161 for the virtualized pci device in this embodiment the virtualized pci device 153 is a device obtained by the vmm 140 virtualizing the hba 119 serving.