[Qemu-devel] Re: [PATCH] Fix non-ACPI Timer Interrupt Routing

["Sebastian Herbszt" <herbszt@gmx.de>]

Beth Kon wrote:
> Sebastian Herbszt wrote:
>> Beth Kon wrote:
>>> This is part of a bigger change for QEMU, incorporating irq0->inti2 
>>> override for ACPI, and non-ACPI, driven by addition of the HPET. It 
>>> required BIOS changes as well as QEMU changes to route irq0 to inti2 
>>> of the IOAPIC. This patch alone is not complete. I have tested the 
>>> complete solution in QEMU, thus the guards.
>>
>> I just tested qemu r7185 with bochs bios (without your patch) and used 
>> a Linux
> Do you mean you used a bochs bios that doesn't include #ifdef BX_QEMU 
> portions?

I was indeed testing pure bochs bios.

> Then it wouldn't work because QEMU overrides irq0->inti2 in 
> its ioapic code and without the matching bios that notifies the guest of 
> the override, boots would likely fail. This change was put in because of 
> the needs of the HPET, but now it is standard procedure for QEMU. With 
> or without HPET, QEMU will override irq0->inti2.

This was the missing piece. I just looked at the change [1] and now it explains
why my testing with pure bochs bios failed. Thanks.
It's also the reason why this change is qemu only. ioapic.cc from bochs doesn't
have such override hard-coded.

> If you mean that you used a QEMU Bochs (with ifdef BX_QEMU included), 
> please let me know what kind of errors you are seeing.

I did just retest with bios.bin from qemu r7055

hpet enabled, no guest kernel parameters
hpet enabled, guest kernel with acpi=off <- hang
hpet disabled, no guest kernel parameters
hpet disabled, guest kernel with acpi=off <- hang

and those two hangs with acpi=off are fixed in r7169.

[1] http://svn.savannah.gnu.org/viewvc/trunk/hw/apic.c?root=qemu&r1=5890&r2=6081

- Sebastian