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

Gerd Hoffmann kraxel at redhat.com
Thu Mar 21 09:18:50 CET 2013

On 03/21/13 07:23, Michael S. Tsirkin wrote:
> 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?

I think we always have a MADT, don't we?  So why worry about the case
that we might have no MADT?  I think the logic is just fine here.

Having a debug printk saying which table came from there would be nice
for trouble shooting though.

>> This also needs
>> to be resolved for SSDT tables, which can have zero, one, or more
>> instances.

Same argument as for the MADT.

> How about we don't bother to determine this at runtime at all?

Because it will be a PITA for testers + developers to figure the correct
.config switches of the day during the transition phase?

>> 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.

Same argument as for the MADT.

>> 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.

As this is quite a bunch of work I would tend to avoid a flag day like
this so we can switch over tables one by one without building up big
patch queues.

Once all is done switched over we can add a .config option for the
seabios acpi table generation code, so it can be turned off altogether
for qemu versions new enougth.


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