Re: [Qemu-devel] Virtual Machine Generation ID

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Oct 04, 2016 at 03:51:40PM -0700, Ed Swierk wrote:
> On Thu, Sep 15, 2016 at 5:36 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Thu, Sep 15, 2016 at 05:23:28PM -0700, Ed Swierk wrote:
> >> I'm wondering what it will take to finish up work on vmgenid.
> >>
> >> https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg05599.html
> >
> > We have ACPI_BUILD_TPMLOG_FILE in tree now and I think it could be
> > allocated in a similar way.
> > Integrate patch "fw-cfg: support writeable blobs" to communicate the
> > allocated address back to QEMU.
> 
> Starting with Igor's last version at
> https://github.com/imammedo/qemu/commits/vmgen_wip , it's not clear to
> me which changes need to be ported, which changes are obsoleted by
> your new fw-cfg stuff and/or upstream churn in ACPI, device
> properties, etc. In particular ACPI is still a total mystery to me,
> though passing a single address from guest to host can't be that hard,
> can it?
> 
> Any clues would be appreciated.
> 
> --Ed

It might be best to just re-start from the beginning.
So the idea is that ACPI should be about supplying the address
to guest. To supply address to host we'll use fw cfg.
This would be new I think:

- add support for writeable fw cfg blobs
- add linker/loader command to write address of a blob into
  such a fw cfg file
- add a new file used for vm gen id, use loader command above
  to pass the address of a blob allocated for it to host
- whenever vm gen id changes, update file, if we have address
  of blob update that as well
- use linker to patch address of blob into acpi as well
  it needs to be in a separate ssdt at top level
  otherwise it's hard to figure out the offset.

This can be reused from one of the previus versions:
- command line, interrupts and commands to update vm gen id

I can help with acpi if all the rest is clear.

-- 
MST