pci: don't skip function 0 occupancy verification for devfn auto assign

When the devfn is already assigned in the command line, the
do_pci_register_device() may verify if the function 0 is already occupied.

However, when devfn < 0, the verification is skipped because it is part of
the last "else if".

For instance, suppose there is already a device at addr=00.00 of a port.

-device pcie-root-port,bus=pcie.0,chassis=115,id=port01,addr=0e.00 \
-device virtio-net-pci,bus=port01,id=vnet01,addr=00.00 \

When 'addr' is specified for the 2nd device, the hotplug is denied.

(qemu) device_add virtio-net-pci,bus=port01,id=vnet02,addr=01.00
Error: PCI: slot 0 function 0 already occupied by virtio-net-pci, new func virtio-net-pci cannot be exposed to guest.

When 'addr' is automatically assigned, the hotplug is not denied. This is
because the verification is skipped.

(qemu) device_add virtio-net-pci,bus=port01,id=vnet02
warning: PCI: slot 1 is not valid for virtio-net-pci, parent device only allows plugging into slot 0.

Fix the issue by moving the verification into an independent 'if'
statement.

Fixes: 3f1e1478db2d ("enable multi-function hot-add")
Reported-by: Aswin Unnikrishnan <aswin.u.unnikrishnan@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Message-Id: <20240708041056.54504-1-dongli.zhang@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

0 files changed, 0 insertions, 0 deletions