[0/2] Fix PIC interrupt handling of x86 CPUs if APIC is globally disabled

Message

Bernhard Beschow Jan. 3, 2024, 8:48 a.m. UTC

This two-patch series is part of my work emulating the VIA Apollo Pro 133T
chipset in QEMU [1] and testing it by running real-world BIOSes on it. The first
patch fixes an issue regarding PIC interrupt handling, the second one just fixes
a typo in a comment.

During testing, I've found that the boot process gets stuck for some BIOSes that
disable the LAPIC globally (by disabling the enable bit in the base address
register). QEMU seems to emulate PIC interrupt handling only if a CPU doesn't
have a LAPIC, and always emulates LAPIC interrupt handling if one is present.
According to the Intel documentation, a CPU should resort to PIC interrupt
handling if its LAPIC is globally didabled. This series fixes this corner case
which makes the boot process succeed. More details can be found in the commit
message.

Testing done:
* `make check`
* `make check-avocado`

[1] https://github.com/shentok/qemu/tree/via-apollo-pro-133t

Bernhard Beschow (2):
  hw/i386/x86: Fix PIC interrupt handling if APIC globally disabled
  target/i386/cpu: Fix small typo in comment

 hw/i386/x86.c     | 10 +++++-----
 target/i386/cpu.c |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)