Hi, > PCI: MMCONFIG at [mem 0xb0000000-0xbfffffff] reserved in E820
Ok, I see you mimic seabios behavior here, resulting in a somewhat odd memory layout (not your fault, of course). Short history lesson: Traditional i440fx memory layout (before we did gigabyte alignment) was memory up to 0xe0000000, pci io space above that. Which caused problems now and then, because it isn't that much address space for pci. So, when figuring how to do things on q35 I wanted more space. Decided to go down to 0xc0000000, giving additional 512m address space for pci. But we also have to place the xbar somewhere. The seabios code to do pci bar placement is somewhat simple and can deal with a single (32bit) I/O window only. Decided to place the xbar @ 0xb0000000, so seabios has a single region above 0xc0000000 for the I/O bars. So, this is where the traditional q35 memory layout with memory up to 0xafffffff comes from. These days it doesn't look that way any more because we added gigabyte alignment meanwhile, so it's this now: low memory 0x00000000 -> 0x7fffffff. free space 0x80000000 -> 0xafffffff, mmcfg xbar 0xb0000000 -> 0xbfffffff, free space 0xc0000000 -> ioapic-base i.e. the xbar splits the free space in a somewhat unclever way. The good news is that xbar location is not fixed. qemu is supposed to check now the firmware programmed the q35 host bridge and fill the acpi tables accordingly, so you should be able to move the xbar to another location. I think there are two reasonable choices: Either 0x80000000 or 0xe0000000. Using 0x80000000 maintains a single I/O window. (above 0x90000000). Gives up backward compatibility to really old (pre gigabyte alignment) q35 machines types. But we are about to drop support for them in upstream qemu anyway, so I'll probably switch seabios to do that. Using 0xe0000000 still splits the I/O address space into two pieces, but I don't think the edk2 resource management code has problems dealing with that. It places the xbar at the highest possible address, so we get a big I/O window below the xbar (and a small one above). The main advantage over using 0xb0000000 is that you can better fit big bars then, for example you can map even a 1G bar (at 0x8000000). cheers, Gerd _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
