Hi folks, I am trying to create a VM that supports hot-plugging a large number of virtio-net-pci device, up to 1000 devices initially.
>From the docs (see below) and from playing with QEMU, it looks like there are >two options. Both with limitations. PCI Express switch It looks like using a PCI Express switch hierarchy is not an option due to bus exhaustion. Each downstream port creates a separate bus and each downstream port only supports hot-plugging a single device. So this gives us a max of 256-ish buses/devices pairs. PCI Root Ports The other option is use a flatter hierarchy, with a number of multi-function PCI Root Ports hanging off 'pcie.0'. However each 'PCI Root Port' can support hot-plugging a single device. So this method really becomes a function of how many free address we have on 'pci.0'. If we make room for say 16 multifunction devices, we get 16*8 ... 128 So ultimately, this will approach will give us a similar to number to using a switch. Is there another method? ( pxb-pcie doesn't support hotplug for instance, and only a single pcie domain is supported qemu ) Thanks, Ray K Pcie.txt, ( https://github.com/qemu/qemu/blob/master/docs/pcie.txt ) Q35 preso ( http://wiki.qemu.org/images/4/4e/Q35.pdf )
