[SeaBIOS] [PATCH 2/2] accept MADT over fw_cfg

Michael S. Tsirkin mst at redhat.com
Thu Mar 21 07:23:48 CET 2013

On Wed, Mar 20, 2013 at 08:22:30PM -0400, Kevin O'Connor wrote:
> On Wed, Mar 20, 2013 at 10:53:05PM +0100, Laszlo Ersek wrote:
> > 
> > Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> I think we need to figure out what the final fw_cfg interface for
> ACPI, SMBIOS, mptable, and PIR will be.
> We can use the current fw_cfg ACPI table passing mechanism for ACPI,
> but there are a couple of things that need to be worked out.  For each
> table, there must be a way to determine if SeaBIOS should build it, or
> if the table should not be present at all.  For example, if MADT isn't
> present in the fw_cfg, is that because SeaBIOS is expected to build it
> or because it is not expected to be present at all?  This also needs
> to be resolved for SSDT tables, which can have zero, one, or more
> instances.

How about we don't bother to determine this at runtime at all?
Long term all tables will be in qemu so why bother with
a runtime mechanism just for an intermediate stage?
Just build BIOS with the correct flags.

> Finally, the mechanism should define how the RSDP
> signatures is set as well as support both RSDT and XSDT tables (with
> signatures defined by QEMU for these as well).
> For SMBIOS, I don't think we should use the existing fw_cfg mechanism.
> It's too complicated for what is needed.  Instead, one fw_cfg "file"
> entry with the whole smbios table should suffice.  For mptable and
> PIR, there is no current mechanism, so we can add new fw_cfg "files"
> for them.  However, for all of these SeaBIOS needs to be able to
> determine when it needs to create the table and when no table should
> be published at all.
> One possible way to accomplish the above would be to add an
> "all_tables_from_qemu" fw_cfg entry that turned off all of the
> existing SeaBIOS code.  There are probably other ways.
> Thoughts?
> -Kevin

Yes I agree these tables need some thought.  But first things first, we
can move quite a lot of code out to qemu with just fw_cfg.


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