Re: [Qemu-devel] Commit 77af8a2b95b79699de650965d5228772743efe84 breaks Windows 2000 support

[Igor Mammedov]

On Tue, 25 Jul 2017 18:23:22 +0200
Paolo Bonzini <address@hidden> wrote:

> On 25/07/2017 18:14, Laszlo Ersek wrote:
> >   "No regressions became apparent in tests with a range of Windows
> >    (XP-10)"
> > 
> > In theory, w2k falls within that range.  
> 
> Nope, Windows 2000 is like NT 5.0, XP is like NT 5.1. :(
> 
> One possibility is to fix it in SeaBIOS instead: if you get a 2.0 FADT
> and an XSDT and no RSDT, it can build an RSDT and a 1.0 FADT itself,
> patching the RSDT to point to it.
> 
> It's a hack, but it's the only place I see to make it "just work".  And
> it could be extended nicely in the future.
> 
> All QEMU would have to do is to provide an XSDT _instead_ of an RSDT.
I'd support it, however it would break migrated guests with old BIOS
image in RAM on reboot.

Legacy users have an option to build SeaBIOS without ACPI from QEMU
support by turning off CONFIG_FW_ROMFILE_LOAD (or use old SeaBIOS)
which leads to using legacy tables included in SeaBIOS.
Then mgmt layer above libvirt which knows what guest OS it's
going to run can pick legacy BIOS image for it.

But the testing issue will still stay as normally it's not tested
path.

PS:
For now we are going to revert PC machine to rev1 and leave q35 at rev3
as Michael suggested to keep both w2k and macos happy.

> 
> Paolo
> 
> > In practice, it is impossible to
> > test *all* Windows versions against ACPI generator changes, even if you
> > try to be thorough (which Phil was). One might not even *know about*
> > "all" Windows versions. So people using w2k and similar should
> > co-maintain the ACPI stuff and report back with testing on the fly;
> > otherwise regressions are impossible to avoid.  
>