hw/i386/x86: Fix PIC interrupt handling if APIC is globally disabled

hw/i386/x86: Fix PIC interrupt handling if APIC is globally disabled

QEMU populates the apic_state attribute of x86 CPUs if supported by real
hardware or if SMP is active. When handling interrupts, it just checks whether
apic_state is populated to route the interrupt to the PIC or to the APIC.
However, chapter 10.4.3 of [1] requires that:

  When IA32_APIC_BASE[11] is 0, the processor is functionally equivalent to an
  IA-32 processor without an on-chip APIC.

This means that when apic_state is populated, QEMU needs to check for the
MSR_IA32_APICBASE_ENABLE flag in addition. Implement this which fixes some
real-world BIOSes.

[1] Intel 64 and IA-32 Architectures Software Developer's Manual, Vol. 3A:
    System Programming Guide, Part 1

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20240106132546.21248-3-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>