Re: [Qemu-devel] [PATCH 1/1] e820: pass high memory too.

[Gerd Hoffmann]

  Hi,

> > > The premise that "this will also allow to pass non-contiguous memory"
> > > is partly false, as you can't use the e820 API below 4g so there's no
> > > way to create non contiguous memory with this mix-cmos-e820-API.
> > 
> > Sure you can.  Why do you think you can't?
> 
> How do you specify an hole below 4g unless you modify seabios first?

First chunk of memory in cmos.
Full list in e820 (first chunk temporarily disabled).

> > That is the goal.  seabios will be fixed to deal with this correctly.
> > I don't want break old seabios versions though (especially not before we
> > have a seabios release which can handle it), so I'll wait with flipping
> > the switch for that.
> 
> Why to ship qemu with an intermediate paravirt protocol?
> 
> And if you don't want to break old seabios I guess you should use a
> new fw_cfg command.

That'll work too.  /me was just trying to avoid having two almost
identical interfaces in fw_cfg.

> Just to show you how flakey this intermediate paravirt interface is,
> assume I boot with -m 1029g.
> [ snip ]

To get more than 1TB work correctly (with all corner cases covered) both
qemu and seabios need to be updated.  No matter whenever we'll go
implement that using cmos, by extending e820 interface or using a new
e820 interface.

>  So "high" is 1g in seabios. So
> RamSizeOver4G is 1g.

Patch to address that exists.

> In short your change is already breaking current seabios.

No.

> When seabios speaks the new paravirt interface, only then modify qemu
> to use the new paravirt interface.

This isn't RHEL.  We can't enforce any ordering with rpm dependencies.

cheers,
  Gerd