Re: [Qemu-devel] [PATCH 1/2] target-i386: disable LINT0 after reset

[Gerd Hoffmann <kraxel@redhat.com>]

On Mi, 2015-09-16 at 07:23 +0200, Jan Kiszka wrote:
> On 2015-09-15 23:19, Alex Williamson wrote:
> > On Mon, 2015-04-13 at 02:32 +0300, Nadav Amit wrote:
> >> Due to old Seabios bug, QEMU reenable LINT0 after reset. This bug is long gone
> >> and therefore this hack is no longer needed.  Since it violates the
> >> specifications, it is removed.
> >>
> >> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
> >> ---
> >>  hw/intc/apic_common.c | 9 ---------
> >>  1 file changed, 9 deletions(-)
> > 
> > Please see bug: https://bugs.launchpad.net/qemu/+bug/1488363
> > 
> > Is this bug perhaps not as long gone as we thought, or is there
> > something else going on here?  Thanks,
> 
> I would say, someone needs to check if the SeaBIOS line that is supposed
> to enable LINT0 is actually executed on one of the broken systems and,
> if not, why not.

There is only one reason (beside miscompiling seabios with
CONFIG_QEMU=n) why seabios would skip acpi initialization, and that is
apic not being present according to cpuid:

    cpuid(1, &eax, &ebx, &ecx, &cpuid_features);
    if (eax < 1 || !(cpuid_features & CPUID_APIC)) {
        // No apic - only the main cpu is present.

https://www.kraxel.org/cgit/seabios/tree/src/fw/smp.c#n79

cheers,
  Gerd

PS: coreboot tripped over this too, fixed just a few days ago.