On Tue, Feb 11, 2014 at 09:54:44PM +0200, Michael S. Tsirkin wrote:
> On Tue, Feb 11, 2014 at 01:23:31PM -0500, Gabriel L. Somlo wrote:
> > I'm trying to get OS X to work as a QEMU guest, and one of the few
> > remaining "mysteries" I need to solve is that the OS X guest hangs
> > during boot, waiting for its boot disk to be available, unless the
> > following KVM patch is applied:
> > [...]
> > 2. Is there anything in QEMU (besides the ACPI DSDT .dsl files) which
> > has a hardcoded assumption re. "polarity == 0", or active-high, for
> > level-triggered interrupts? I tried to dig through hw/i386/kvm/ioapic.c
> > and a bunch of other files, but couldn't isolate anything that I could
> > "flip" to fix things in userspace.
> >
> >
> > Any ideas or suggestions about the appropriate way to move forward would
> > be much appreciated !!!
> >
> >
> > Thanks much,
> > --Gabriel
>
> I think changing ACPI is the right thing to
> do really. But we'll need to fix some things
> first of course.
>
> I think it's PC Q35 that has this assumption.
> hw/i386/pc_q35.c
>
> gsi = qemu_allocate_irqs(kvm_pc_gsi_handler, gsi_state,
> GSI_NUM_PINS);
>
> kvm_pc_gsi_handler simply forwards interrupts to kvm.
>
> and
>
> hw/isa/lpc_ich9.c
> static void ich9_lpc_update_pic(ICH9LPCState *lpc, int pic_irq)
> {
> int i, pic_level;
>
> /* The pic level is the logical OR of all the PCI irqs mapped to it */
> /* The pic level is the logical OR of all the PCI irqs mapped to it
> * */
> pic_level = 0;
> for (i = 0; i < ICH9_LPC_NB_PIRQS; i++) {
> int tmp_irq;
> int tmp_dis;
> ich9_lpc_pic_irq(lpc, i, &tmp_irq, &tmp_dis);
> if (!tmp_dis && pic_irq == tmp_irq) {
> pic_level |= pci_bus_get_irq_level(lpc->d.bus, i);
> }
> }
>
> so somewhere we need to flip it, I am guessing in ich9
> along the lines of:
>
> - pic_level = 0;
> - pic_level |= pci_bus_get_irq_level(lpc->d.bus, i);
> + pic_level = 1;
> + pic_level &= !pci_bus_get_irq_level(lpc->d.bus, i);
I think now we're on to something!
I managed to boot OS X on q35 with absolutely no kernel patches, but
Linux still hated it ("irqXX: nobody cared"). At least now I know what
I'm looking for, so I'll try to come up with a way to flip
level-triggered polarity to ActiveLow across all of i386, in a way
that works for Linux and Windows guests as well.
Thanks again for getting me unstuck!
--Gabriel
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