Re: [RFC PATCH] hw/i386/e820: remove legacy reserved entries for e820

[Ani Sinha]

On Thu, Mar 10, 2022 at 10:12 PM Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Thu, 10 Mar 2022 11:51:37 +0530
> Ani Sinha <ani@anisinha.ca> wrote:
>
> > On Mon, Feb 28, 2022 at 8:56 PM Ani Sinha <ani@anisinha.ca> wrote:
> > >
> > > e820 reserved entries were used before the dynamic entries with fw config 
> > > files
> > > were intoduced into qemu with the following change:
> > > 7d67110f2d9a6("pc: add etc/e820 fw_cfg file")
> > >
> > > Identical support was introduced into seabios as well with the following 
> > > commit:
> > > ce39bd4031820 ("Add support for etc/e820 fw_cfg file")
> > >
> > > Both the above commits are now quite old. Seabios uses fw config files and
> > > dynamic e820 entries by default and only falls back to using reserved 
> > > entries
> > > when it has to work with old qemu (versions earlier than 1.7). Please see
> > > functions qemu_cfg_e820() and qemu_early_e820(). It is safe to remove 
> > > legacy
> > > FW_CFG_E820_TABLE and associated code. It would be incredibly rare to run 
> > > the
> > > latest qemu version with a very old version of seabios that did not 
> > > support
> > > fw config files for e820.
> > >
> > > As far as I could see, edk2/ovfm never supported reserved entries and 
> > > uses fw
> > > config files from the beginning. So there should be no incompatibilities 
> > > with
> > > ovfm as well.
> >
> > Igor, Gerd, as I had replied in the other thread, I am not sure if we
> > need the compatibility dance in order to do this. I think we can't
> > carry this legacy stuff on forever.
> > Please advice.
>
> see commit 7d67110f2d
> until we have older machine types it must stay or have a compat knob,
> once they are gone we can remove it as 1.7 and older machine types
> are supposed to have newer SeaBIOS version that doesn't utilize
> it anymore.
>
> so add a compat knob (not sure if it's worth the trouble) or
> wait till pre 1.7 machines are gone and then rebase/repost.

Ok fine,. I will wait till 7.0 is released at which point
pc-1440fx-1.7 machine will be deprecated.
I will repost it again after that.