Re: libxl - b_info.{acpi,apic} behaves differently than b_info.u.hvm.{acpi,apic}

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.09.2020 05:57, Marek Marczykowski-Górecki wrote:
> After updating from Xen 4.13 to Xen 4.14 I have troubles starting any
> HVM: just after hvmloader saying "Invoking SeaBIOS" I get "(XEN) MMIO
> emulation failed (1): d29v0 32bit @ 0008:fffeedf d -> "
> 
> I come to a situation where seemingly the same domU started via xl
> works, while when started via libvirt it crashes. This seems to be
> related to xl setting b_info.{acpi,apic}, while libvirt setting
> b_info.u.hvm.{acpi,apic}. Modifying libvirt to use the former fixes the
> issue.
> 
> So, handling the old option got broken sometime between 4.13 and 4.14.

The respective changes in libxl date back to 2016/2017, and the involved
code looks identical between 4.13 and 4.14. Perhaps there's some 4.13-
only logic in libvirt, which really means to be >= 4.13? In any event
libxl_types.idl clearly says the two u.hvm fields are deprecated;
nevertheless there are some uses left for u.hvm.acpi (the most
suspicious one in xl_sxp.c) and exactly one in a comment for u.hvm.apic.
Sadly this marking of being deprecated doesn't get reflected in the
_libxl_types.h which gets installed for public consumption.

Jan