Re: [Qemu-devel] KVM call agenda for 2013-05-28

[Michael S. Tsirkin]

On Tue, May 28, 2013 at 07:53:09PM -0400, Kevin O'Connor wrote:
> On Thu, May 23, 2013 at 03:41:32PM +0300, Michael S. Tsirkin wrote:
> > Juan is not available now, and Anthony asked for
> > agenda to be sent early.
> > So here comes:
> > 
> > Agenda for the meeting Tue, May 28:
> > 
> > - Generating acpi tables
> 
> I didn't see any meeting notes, but I thought it would be worthwhile
> to summarize the call.  This is from memory so correct me if I got
> anything wrong.
> 
> Anthony believes that the generation of ACPI tables is the task of the
> firmware.  Reasons cited include security implications of running more
> code in qemu vs the guest context, complexities in running iasl on
> big-endian machines,

Forgot to mention: my patchset actually solves this by keeping
pre-generated ACPI tables in QEMU.  This means you need to have iasl to
do ACPI development but that's nothing new.

However, generating the tables in QEMU actually opens up the possibility
of linking in a library for generating ACPI tables, if such surfaces,
and dropping the iasl dependency.

While my patchset does not do this, it's not unheard of.

This would not be practical for bios.

> possible complexity of having to regenerate
> tables on a vm reboot, overall sloppiness of doing it in QEMU.  Raised
> that QOM interface should be sufficient.
> 
> Kevin believes that the bios table code should be moved up into QEMU.
> Reasons cited include the churn rate in SeaBIOS for this QEMU feature
> (15-20% of all SeaBIOS commits since integrating with QEMU have been
> for bios tables; 20% of SeaBIOS commits in last year), complexity of
> trying to pass all the content needed to generate the tables (eg,
> device details, power tree, irq routing), complexity of scheduling
> changes across different repos and synchronizing their rollout,
> complexity of implemeting the code in both OVMF and SeaBIOS.  Kevin
> wasn't aware of a requirement to regenerate acpi tables on a vm
> reboot.
> 
> There were discussions on potentially introducing a middle component
> to generate the tables.  Coreboot was raised as a possibility, and
> David thought it would be okay to use coreboot for both OVMF and
> SeaBIOS.  The possibility was also raised of a "rom" that lives in the
> qemu repo, is run in the guest, and generates the tables (which is
> similar to the hvmloader approach that Xen uses).
> 
> Anthony requested that patches be made that generate the ACPI tables
> in QEMU for the upcoming hotplug work, so that they could be evaluated
> to see if they truly do need to live in QEMU or if the code could live
> in the firmware.  There were no objections.
> 
> -Kevin