Re: [Qemu-devel] pci irq confusion

["M. Warner Losh" <imp@bsdimp.com>]

In message: <9ae48b020905181024p15b3207fy7ea7eb62b868ec0b@mail.gmail.com>
            Ed Swierk <eswierk@aristanetworks.com> writes:
: On Fri, May 15, 2009 at 1:39 AM, Gerd Hoffmann <kraxel@redhat.com> wrote:
: > 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?
: 
: qemu's "info pci" monitor command gets the IRQ value from offset 0x3c
: in the device's PCI config space, which is a useless scratch register.
: Some BIOSes may write to this register the actual IRQ assigned to the
: device, but many don't, and I don't know of any OS that relies on it.
: IMHO this IRQ value is misleading and shouldn't be reported by qemu at
: all.

I know that all the BSDs (and I thought Linux) require the scratch
register to be correct, if it isn't 0xff...

Warner