On Fri, Jan 17, 2014 at 07:43:30PM +0900, eiichiro.oiwa.nm@xxxxxxxxxxx wrote: > Because legacy VGA is only one device on x86 System, I think qemu has to emulate a bridge > for legacy VGA. The VGA Enable bit on its bridge control register has to set to 1. The VGA > Enable bit describes in Table 3-10 Bridge Control register. When there are two VGA cards > on the same system, I think its system needs two bridges for each device. These bridges > need bridge control registers. One VGA Enable bit on its bridge for legacy VGA has to set > to 1. Another VGA Enable bit for second VGA has to set to 0. > > > >On Thu, Jan 16, 2014 at 7:16 PM, <eiichiro.oiwa.nm@xxxxxxxxxxx> wrote: > >> I think qemu is breaking "PCI-to-PCI Bridge Architecture Specification Revison 1.2 > >> June 9, 2003 Chapter 12. VGA Support". > > > >And what exactly do you think qemu is doing wrong? Chapter 12 is ten > >pages long. Is there something there that prohibits two VGA devices > >on the same bus? I'm not a qemu developer, but if I were, I would > >need a better hint about what is wrong before I could fix it. > > > >Again, sorry if you said this already and I missed it. > > > >>>[+cc Michael, Jesse, David, qemu-devel] > >>> > >>>On Wed, Jan 15, 2014 at 8:58 PM, <eiichiro.oiwa.nm@xxxxxxxxxxx> wrote: > >>>> I suggest you should not break the PCI specification, as a developer of proprietary > >>>> hypervisor, but I think your patch is no problem. > >>>> Your PCI structure is specialized structure for your virtual machine. > >>>> Maybe, your virtual machine will be causing another problem on Linux or other kernels > >>>> because of breaking the PCI specification. > >>> > >>>I assume you think qemu is breaking the PCI spec. What exactly do you > >>>think is broken? Please give specific references to the spec. This > >>>conversation is pretty fragmented, and I came in late, so I apologize > >>>if I missed this. > >>> > >>>Bjorn > >>> > > None of the bridges included in QEMU implements VGA support. The spec explicitly says its optional, so that's ok. As a result, you need to put device which has to work in VGA mode on the root bus, any device behind a bridge won't work in VGA mode (but might work in non VGA mode). -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
