On Thu, May 30, 2013 at 7:34 PM, Kevin O'Connor email@example.com wrote:
On Tue, May 28, 2013 at 07:53:09PM -0400, Kevin O'Connor wrote:
There were discussions on potentially introducing a middle component to generate the tables. Coreboot was raised as a possibility, and David thought it would be okay to use coreboot for both OVMF and SeaBIOS. The possibility was also raised of a "rom" that lives in the qemu repo, is run in the guest, and generates the tables (which is similar to the hvmloader approach that Xen uses).
Given the objections to implementing ACPI directly in QEMU, one possible way forward would be to split the current SeaBIOS rom into two roms: "qvmloader" and "seabios". The "qvmloader" would do the qemu specific platform init (pci init, smm init, mtrr init, bios tables) and then load and run the regular seabios rom. With this split, qvmloader could be committed into the QEMU repo and maintained there. This would be analogous to Xen's hvmloader with the seabios code used as a starting point to implement it.
I think hvmloader is more closely tied to Xen, than the Xen firmware. I could be wrong, but thought it could do things like add memory to guest machine. ?? I don't think this model is analogous to Xen's model. I view the hvmloader as just a part of Xen. (Not part of the 'firmware' stack.)
In adding this pre-firmware firmware, wouldn't Anthony's concern of iasl still be an issue?
Why is updating the ACPI tables in seabios viewed as such a burden? Either qemu does it, or seabios... (And, OVMF too, but I don't think you guys are concerned with that. :)
On the flip side, why is moving the ACPI tables to QEMU such an issue? It seems like Xen and virtualbox both already do this. Why is running iasl not an issue for them?
I think overall I prefer the tables being built in the firmware, despite the extra thrash. Some things, such as the addresses where devices are configured at are re-programmable in QEMU, so a firmware can decide to use a different address, and thus invalidate the address qvmloader had set in the tables.
Maybe we are doing lots of things horribly wrong in our OVMF ACPI tables :), but I haven't seen it as much of a burden. (Of course, Laszlo has helped out with many of the ACPI changes in OVMF, so his opinion should be taken into consideration too. :)