On Tue, 26 Dec 2023 10:30:04 +0800 Wu Zongyong <wuzongyong@xxxxxxxxxxxxxxxxx> wrote: > Hi, > > For vfio, I know there are two method to get region size: > 1. VFIO_DEVICE_GET_REGION_INFO ioctl > 2. write a value of all 1's to the bar register of vfio-device fd > and then read the value back which is described in pci spec > > Now I am curious about is it a must for a vfio-mdev parent driver to > implement the method 2? Or it is just a optional interface. If there's not a working, compliant config space, the device shouldn't claim to implement a vfio-pci interface. There's vfio-platform available for non-PCI devices. While the BAR size may be found via either REGION_INFO or config space itself, the BAR address space is only found via config space, ie. memory or IO, 32 or 64-bit, prefetchable or not. Thanks, Alex
