On Wed, Jun 25, 2014 at 10:28:21AM +0800, Chen, Tiejun wrote: > On 2014/6/24 10:59, Zhenyu Wang wrote: > >On 2014.06.19 17:53:51 +0800, Tiejun Chen wrote: > >>Originally the reason to probe ISA bridge instead of Dev31:Fun0 > >>is to make graphics device passthrough work easy for VMM, that > >>only need to expose ISA bridge to let driver know the real > >>hardware underneath. This is a requirement from virtualization > >>team. Especially in that virtualized environments, XEN, there > >>is irrelevant ISA bridge in the system with that legacy qemu > >>version specific to xen, qemu-xen-traditional. So to work > >>reliably, we should scan through all the ISA bridge devices > >>and check for the first match, instead of only checking the > >>first one. > >> > >>But actually, qemu-xen-traditional, is always enumerated with > >>Dev31:Fun0, 00:1f.0 as follows: > >> > >>hw/pt-graphics.c: > >> > >>intel_pch_init() > >> | > >> + pci_isa_bridge_init(bus, PCI_DEVFN(0x1f, 0), ...); > >> > >>so this mean that isa bridge is still represented with Dev31:Func0 > >>like the native OS. Furthermore, currently we're pushing VGA > >>passthrough support into qemu upstream, and with some discussion, > >>we wouldn't set the bridge class type and just expose this devfn. > >> > >>So we just go back to check devfn to make life normal. > >> > >>Signed-off-by: Tiejun Chen <tiejun.c...@intel.com> > > > >This was added historically when supporting graphics device passthrough. > >Looks qemu upstream can't accept multiple ISA bridge and our PCH is always > >on device 31: func0 as far as I know. Looks good to me. > > > >Reviewed-by: Zhenyu Wang <zhen...@linux.intel.com> > > > > Thanks for your review. > > Do you know when this can be applied?
I'll hold off merging until we have buy-in from upstream quemu on a given approach (which should work for both linux and windows). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
