[SeaBIOS] [PATCH RFC 00/13] qemu: generate acpi tables for the guest
anthony at codemonkey.ws
Tue May 14 15:34:43 CEST 2013
"Michael S. Tsirkin" <mst at redhat.com> writes:
> On Mon, May 13, 2013 at 03:38:51PM -0500, Anthony Liguori wrote:
>> I don't think it's a good idea to move BIOS functionality in QEMU.
> Just to clarify: generating ACPI tables is not BIOS
> functionality. It ended up in seabios for historical
> A normal scenario for ACPI tables is that they are written
> in ASL and compiled with IASL.
I wouldn't call this the normal scenario. Some tables are static but
more tables are dynamic than you'd think. If you're a firmware engineer
and you have to support dozens of platforms, it's much easier to make
the tables dynamic than attempt to maintain dozens of ASL descriptions.
A lot of what you'd consider to be static is actually dynamic in a
> The tables are then stored
> in some ROM device - most of them, except FACP, can actually
> be mapped directly from ROM if necessary.
> You won't normally find real BIOS probing PCI slots for
> hotplug support and writing EJ0 methods dynamically -
> instead the assumption is that hardware (in this case QEMU)
> supplies its own static description in form of ACPI tables.
Actually, this is a very good example. In more modern boxes like Flex,
there's a PCI-Express backplane that all of the nodes are connected to
with a common set of slots for all nodes. You can configure in firmware
how the slots map to each node.
I can share an acpi dump from one of these systems when after I head
into the office this morning.
This is what's nice about a switched PCI complex. You have tremendous
amounts of flexibility in how you set things up.
> My patchset uses FW_CFG as such a ROM device. It would be
> easy to switch to something else instead of FW_CFG.
> Is this what you are suggesting?
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