On Fri, Sep 18, 2020 at 08:34:37AM -0400, Michael S. Tsirkin wrote: > On Fri, Sep 11, 2020 at 10:00:31AM -0700, Sean Christopherson wrote: > > On Mon, Sep 07, 2020 at 07:32:23AM -0400, Michael S. Tsirkin wrote: > > > I suspect microvms will need pci eventually. I would much rather KVM > > > had an exit-less discovery mechanism in place by then because > > > learning from history if it doesn't they will do some kind of > > > hack on the kernel command line, and everyone will be stuck > > > supporting that for years ... > > > > Is it not an option for the VMM to "accurately" enumerate the number of buses? > > E.g. if the VMM has devices on only bus 0, then enumerate that there is one > > bus so that the guest doesn't try and probe devices that can't possibly exist. > > Or is that completely non-sensical and/or violate PCIe spec? > > > There is some tension here, in that one way to make guest boot faster > is to defer hotplug of devices until after it booted. Sorry, I didn't follow that, probably because my PCI knowledge is lacking. What does device hotplug have to do with the number of buses enumerated to the guest?
