Re: [Qemu-devel] [PATCH RFC 0/3] seabios: move acpi table formatting out of bios

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Apr 25, 2013 at 12:02:20PM +0300, Michael S. Tsirkin wrote:
> 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.

After some thought, there are two additional
options worth considering, in that they simplify
bios code somewhat:

- bios could get size from qemu, allocate a buffer
  (e.g. could be one buffer for all tables)
  and pass the address to qemu.
  qemu does all the patching

- further, qemu could do the copy of tables into
  that address directly


thoughts?



> 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
> 
> -- 
> MST
> 
> 
> Michael S. Tsirkin (3):
>   linker: utility to patch in-memory ROM files
>   acpi: load and link tables from /etc/acpi/
>   acpi: add an option to disable builtin tables
> 
>  Makefile     |  2 +-
>  src/Kconfig  | 12 +++++++-
>  src/acpi.c   | 67 +++++++++++++++++++++++++++++++++++++++++++-
>  src/linker.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  src/linker.h | 50 +++++++++++++++++++++++++++++++++
>  src/util.h   |  1 +
>  6 files changed, 219 insertions(+), 3 deletions(-)
>  create mode 100644 src/linker.c
>  create mode 100644 src/linker.h
> 
> -- 
> MST