Il 10/12/2013 18:46, Laszlo Ersek ha scritto: > On 12/10/13 16:53, Gerd Hoffmann wrote: >> On Di, 2013-12-10 at 16:47 +0100, Laszlo Ersek wrote: >>> On 12/10/13 15:53, Gerd Hoffmann wrote: >>>> Hi, >>>> >>>>> If we could make a small guset visible change, it would be simpler to >>>>> always make the PCI hole 1GB in size; it is currently 256MB for i440FX >>>>> and 1.25GB for q35. >>>> >>>> Easy for i440fx. >>> >>> I think it's going to break OVMF again. >> >> Can't see a reason why it should. > > PCI enumeration in OVMF assigns resources from a window that starts > exactly above the end of below-4gb-memory. For example, in case of a > 2.5GB guest, the frame buffer bar of cirrus can be somewhere just above > 2.5GB. > > If you change the PCI hole in qemu so that it will start at 3GB, always, > then the ACPI tables exported by qemu will also advertise the big mmio > range starting at 3GB. OVMF will pass those tables through to the OS. > Accordingly, the OS will try to access the framebuffer above 3GB, but > OVMF has configured that bar between 2.5GB and 3GB.
Right, you explained that in the past. No need to worry, this would be just for >3GB guests. Paolo > IOW, I think this proposal would undo your [PATCH v2] piix: fix 32bit > pci hole. > > I can of course live with whatever PCI hole as long as it is made > available to OVMF through an easy-to-parse fw_cfg file. Then I can sync > the OVMF enumeration to qemu's preference. > > The fw_cfg file "etc/pci-info" allowed me to do exactly that. But it has > been killed. I'd like it to be resurrected, even if SeaBIOS ignores it. > > Thanks, > Laszlo >
