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Description of problem:
guest cannot find disk  via -hdb with "-M q35". But with "-device ide-drive", guest can r/w this disk well. 
BTW, with "-M pc", guest can r/w this disk(-hdb /home/scalability/disk30) well.
So if "-M q35" doesn't support -hdb, could give some warning or error message. 

Version-Release number of selected component (if applicable):
seabios-1.7.2.2-10.el7.x86_64
qemu-kvm-rhev-1.5.3-37.el7.x86_64
3.10.0-67.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Boot guest with the following cli.
# /usr/libexec/qemu-kvm  -drive file=rhel7_64.qcow2_v3,if=none,format=qcow2,id=sysdirve,cache=none -device ide-drive,bus=ide.0,drive=sysdirve,id=sysimg,bootindex=4 -M q35 -boot menu=on,reboot-timeout=-1,strict=on  -hdb  /home/scalability/disk30
2.
3.

Actual results:
can not find disk "-hdb".

Expected results:
if "-M q35" doesn't support -hdb, could give some warning or error message.

Additional info:
seabios can not find "-hdb" disk, but can find "-device ide-drive" disk with "-M q35".

Can confirm this on upstream qemu; it's not just seabios - the drive isn't visible to the guest at all, and there are no warnings/errors.

Checked with kwolf; -hdb isn't expected to work on q35 - but it should give you some diagnostics.

-drive if=ide,... and its sugared forms -cdrom, -hda, ... do not yet work with Q35.  Marking duplicate of bug 946993, which has more detail.

*** This bug has been marked as a duplicate of bug 946993 ***