Untested yet, but I thought I'd share the BIOS bits so we can agree on direction.
In particular check out ROM sizes: - Before patchset with DSDT enabled Total size: 127880 Fixed: 59060 Free: 3192 (used 97.6% of 128KiB rom) - Before patchset with DSDT disabled Total size: 122844 Fixed: 58884 Free: 8228 (used 93.7% of 128KiB rom) - After patchset: Total size: 128776 Fixed: 59100 Free: 2296 (used 98.2% of 128KiB rom) - Legacy disabled at build time: Total size: 119836 Fixed: 58996 Free: 11236 (used 91.4% of 128KiB rom)
As can be seen from this, most size savings come from dropping DSDT, but we do save a bit by removing other tables. Of course the real reason to move tables to QEMU is so that ACPI can better match hardware.
This patchset adds an option to move all code for formatting acpi tables out of BIOS. With this, QEMU has full control over the table layout. All tables are loaded from the new "/etc/acpi/" directory. Any entries in this directory cause BIOS to disable ACPI table generation completely. A generic linker script, controlled by QEMU, is loaded from "/etc/linker-script". It is used to patch in table pointers and checksums.
BIOS still has limited ability to parse the tables, for the following purposes: - locate resume vector - allocate RSDP in FSEG - allocate FACS at an aligned address