Re: [Qemu-devel] Attaching PCI devices to the PCIe root complex

[Michael S. Tsirkin]

On Mon, Sep 30, 2013 at 06:01:17PM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > Yes but, same as in the initial design,
> > it really makes it user's problem.
> > 
> > So we'd have
> > virtio-net-pci-conventional
> > virtio-net-pci-express
> > virtio-net-pci-integrated
> > 
> > 
> > All this while users just really want to say "virtio"
> > (that's the expert user, what most people want is for guest to be faster).
> 
> And for the actual device emulation it makes almost no difference.  xhci
> exists in express and integrated variants too.  The qemu-emulated device
> calls pcie_endpoint_cap_init() unconditionally, so the express endpoint
> capability shows up even if you plug it into the root bus.  That should
> be handled better.  But I think that would be the only difference in the
> xhci code.  And even that could be handled in the pci core, for example
> by making pcie_endpoint_cap_init a nop unless the device is actually is
> a express endpoint from the bus topology point of view.
> 
> Maybe PCIDeviceClass->is_express should move to PCIDevice and
> PCIDeviceClass should get a supports_express field instead.
> 
> cheers,
>   Gerd

Not sure why do you need is_express in PCIDevice.
We already have QEMU_PCI_CAP_EXPRESS set in cap_present.