Am 30.01.2013 17:33, schrieb Anthony Liguori: > Gerd Hoffmann <kraxel@xxxxxxxxxx> writes: > >>> hw/qxl.c: portio_list_add(qxl_vga_port_list, >>> pci_address_space_io(dev), 0x3b0); >>> hw/vga.c: portio_list_add(vga_port_list, address_space_io, 0x3b0); >> >> That reminds me I should solve this in a more elegant way. >> >> qxl takes over the vga io ports. The reason it does this is because qxl >> switches into vga mode in case the vga ports are accessed while not in >> vga mode. After doing the check (and possibly switching mode) the vga >> handler is called to actually handle it. > > The best way to handle this would be to remodel how we do VGA. > > Make VGACommonState a proper QOM object and use it as the base class for > QXL, CirrusVGA, QEMUVGA (std-vga), and VMwareVGA. That would require polymorphism since we already need to derive from PCIDevice or ISADevice respectively for interfacing with the bus... Modern object-oriented languages have tried to avoid multi-inheritence due to arising complications, I thought. Wouldn't object if someone wanted to do the dirty implementation work though. ;) Another such example is EHCI, with PCIDevice and SysBusDevice frontends, sharing an EHCIState struct and having helper functions operating on that core state only. Quite a few device share such a pattern today actually (serial, m48t59, ...). > The VGA accessors should be exposed as a memory region but the sub class > ought to be responsible for actually adding it to a subregion. > >> >> That twist makes it a bit hard to convert vga ... >> >> Anyone knows how one would do that with the memory api instead? I think >> taking over the ports is easy as the memory regions have priorities so I >> can simply register a region with higher priority. I have no clue how to >> forward the access to the vga code though. >> > > That should be possible with priorities, but I think it's wrong. There > aren't two VGA devices. QXL is-a VGA device and the best way to > override behavior of base VGA device is through polymorphism. In this particular case QXL is-a PCI VGA device though, so we can decouple it from core VGA modeling. Placing the MemoryRegionOps inside the Class (rather than static const) might be a short-term solution for overriding read/write handlers of a particular VGA MemoryRegion. :) Cheers, Andreas > This isn't really a memory API issue, it's a modeling issue. > > Regards, > > Anthony Liguori > >> Anyone has clues / suggestions? >> >> thanks, >> Gerd -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
