[Qemu-devel] Re: [SeaBIOS] [PATCHv2] load hpet info for HPET ACPI table from qemu

[Kevin O'Connor <kevin@koconnor.net>]

On Mon, Jun 14, 2010 at 09:56:15PM +0300, Gleb Natapov wrote:
> On Mon, Jun 14, 2010 at 02:25:21PM -0400, Kevin O'Connor wrote:
> > It seems there was a change in qemu to the hpet functionality.
> My patch is completely unrelated to functionality change in qemu. In
> fact I wrote it before the change and had to rebase. Seabios/qemu have
> a bug that HPET is always advertise through ACPI table even when qemu
> haven't created one. So your description above is not accurate.

I apologize for the confusion.  However, I feel this only furthers my
proposal.  (There was a defect in hpet table generation - seabios
knows/cares nothing about the hpet - but now we need to review, patch,
and coordinate two different projects.)

> But even if it was accurate propagation features through software stack is
> common operation everywhere. Think about adding system call to the
> kernel and updating libc, or adding feature to kvm kernel module and
> adding patch to use it in qemu.

I don't see why the above would deter us from optimizing seabios/qemu
maintenance work.

> > I'm not suggesting a radical rethink of fwcfg, but I fail to see the
> > advantage in introducing the arbitrary "struct hpet_fw_entry" when
> > there is a perfectly good, well defined, "struct acpi_20_hpet" that
> > already exists.  This new arbitrary intermediate format just
> > introduces "make work" for all of us.
> > 
> Then qemu will have to create ACPI header too and will have to fill
> details like oem_id/oem_table_id and so on. Now if I want to change them
> in my bios version it is not enough to edit CONFIG_APPNAME in seabios.

Easily solved - if there exists a table via
qemu_cfg_acpi_additional_tables(), then SeaBIOS could use the oem_ids
from that table for all tables SeaBIOS creates.

> If seabios will decide to move to more resent version of ACPI spec it
> will not be able to do so since it will not fully control table creation.

Well, SeaBIOS already doesn't fully control table creation.

But.. in order to move to a newer ACPI spec, there would be qemu
changes anyway.  (If nothing else, so that qemu can tell seabios if
it's okay to use the new rev.)  At that point we're stuck changing
both repos anyway - nothing gained, nothing lost.

I still think there is an opportunity to reduce the load on the bulk
of acpi changes - most of these changes have no dependence on seabios
at all.

-Kevin