[Qemu-devel] pci irq confusion

[Gerd Hoffmann]

  Hi,

I've looked at the pci irqs for my virtual machine and figured it isn't 
consistent.  Look:

This is what the "info pci" monitor command prints (trimmed a bit for 
better readability):

(qemu) info pci
  Bus  0, device   1, function 2:
    USB controller: PCI device 8086:7020
      IRQ 9.
  Bus  0, device   1, function 3:
    Bridge: PCI device 8086:7113
      IRQ 11.
  Bus  0, device   3, function 0:
    Class ff80: PCI device 5853:0001
      IRQ 11.
  Bus  0, device   4, function 0:
    SCSI controller: PCI device 1000:0012
      IRQ 9.
  Bus  0, device   5, function 0:
    Storage controller: PCI device 1af4:1001
      IRQ 11.
  Bus  0, device   6, function 0:
    RAM controller: PCI device 1af4:1002
      IRQ 9.

This is what lspci says (also trimmed):

00:01.2 USB Controller: Intel Corporation 82371SB PIIX3 USB 
[Natoma/Triton II] (rev 01) (prog-if 00 [UHCI])
        Flags: bus master, fast devsel, latency 64, IRQ 9

00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
        Flags: medium devsel, IRQ 9

00:03.0 Class ff80: XenSource, Inc. Xen Platform Device (rev 01)
        Flags: fast devsel, IRQ 11

00:04.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a
        Flags: bus master, fast devsel, latency 255, IRQ 9

00:05.0 Mass storage controller: Qumranet, Inc. Virtio block device
        Flags: fast devsel, IRQ 10

00:06.0 RAM memory: Qumranet, Inc. Unknown device 1002
        Flags: fast devsel, IRQ 9

And finally the output from /proc/interrupts (i.e. what irq the drivers 
are registered for):

  9:     197541   IO-APIC-level  uhci_hcd:usb1, virtio1, sym53c8xx
 10:        224   IO-APIC-level  virtio0
 11:       2159   IO-APIC-level  acpi, xen-platform-pci

Putting the three info sources into a table gives this picture:

                        |  qemu  |  lspci  |  driver
------------------------+--------+---------+----------
00:01.2  usb            |    9   |     9   |     9
00:01.3  acpi           |   11   |     9   |    11
00:03.0  xen-platform   |   11   |    11   |    11
00:04.0  scsi           |    9   |     9   |     9
00:05.0  virtio-blk     |   11   |    10   |    10
00:06.0  virtio-baloon  |    9   |     9   |     9

Note the inconsistencies for acpi and virtio-blk.  Where do they come 
from?  Is that normal?  Or is that something which needs fixing?

cheers,
  Gerd