[kvm-ppc-devel] PCI interrupts

[kvm-ppc-devel] PCI interrupts

[Hollis Blanchard]

Despite the fact that we seem to have UART interrupts going missing, I
tried playing with attaching a qemu PCI device (rtl8139) to a KVM 440
guest to see what would happen. First though I had to fix some poorly
considered endian-handling qemu code, but after that "ip=dhcp" kernel
parameter still doesn't work (ifup succeeds; DHCP fails).

Debugging reveals that slirp (qemu's "user networking") does in fact see
the DHCP request, and the rtl8139 code does in fact see the reply, but
somehow qemu and the guest seem to disagree about which IRQ to expect
the interrupt on. Hacking it so that they agree doesn't seem to fix the
problem either, so right now I'm digging in to qemu's UIC emulation to
see if there's an issue there. Right now I'm not certain if the guest is
properly setting polarity (UIC0_PR), but more investigation is needed.

Anyways, as an alternative for now, we may be able to get VirtIO working
if we add a polling mode. It might be as easy as setting up a timer in
virtio_pci.c that calls vp_interrupt() directly...

-- 
Hollis Blanchard
IBM Linux Technology Center


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