In the following code, msi lower address, higher address and data is written to msi_desc corresponding to a msi vector. http://lxr.free-electrons.com/source/drivers/pci/msi.c#L311 We can get the msi message from irq using irq_get_msi_desc(). http://lxr.free-electrons.com/source/drivers/pci/msi.c#L349 struct msi_desc *entry = irq_get_msi_desc(irq); Regards Manoj Nayak