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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

Adding toolstack maintainers.

On Thu, Sep 10, 2020 at 12:29:21PM +0200, Marek Marczykowski-Górecki wrote:
> On Thu, Sep 10, 2020 at 10:51:48AM +0200, Roger Pau Monné wrote:
> > On Thu, Sep 10, 2020 at 05:57:23AM +0200, Marek Marczykowski-Górecki wrote:
> > > Hi,
> > > 
> > > 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.
> > 
> > Could you print the values of the involved fields at the end of
> > libxl__domain_build_info_setdefault in both cases?
> > 
> > I'm not able to spot what changed between 4.13 and 4.14 that could
> > alter the behavior, but knowing the values at that point might make
> > it easier.
> 
> Sure, will do.
> It may be also something else: maybe it acpi/apic settings were broken
> before, but did not results in a domU crash this way.
> FWIW when looking into /var/lib/xen/*-libxl-json I clearly see
> difference between b_info.{acpi,apic} and b_info.u.hvm.{acpi,apic}.

I think libxl__domain_build_info_setdefault should check whether
b_info.u.hvm.{acpi,apic} is set and copy those into b_info.{acpi,apic}
if those are not set?

Toolstack people is more likely to have an opinion here, or to help
debug the issue.

> > > So, handling the old option got broken sometime between 4.13 and 4.14.
> > > Or perhaps it is some other related side effect.
> > 
> > Libvirt master tests seem to have been failing for some time (60 days)
> > in the build phase [0], maybe you are using a newer version of libvirt
> > than what osstest is currently testing? (Xen flights are currently
> > stuck at libvirt commit 2c846fa6bcc11929c9fb857a22430fb9945654ad).
> 
> I use libvirt 6.6.0, so even older one, and in fact updated it from
> 6.4.0 together with Xen 4.14. But I don't see relevant change between
> those two versions.
> 
> BTW The libvirt build may require more attention, they've changed build
> system... Now it is built with meson/ninja (haven't figured it out yet).

If you can figure out and send a patch to fix oostest that would be
great!

Thanks, Roger.