Created attachment 711808 [details]
AHCI screenshot.

Created attachment 711809 [details]
IDE screenshot.

Created attachment 711810 [details]
SCSI screenshot.

multiple hard disks using AHCI (Q35) also hit this issue.

# /usr/libexec/qemu-kvm -S -M q35...-drive file=/home/my-data-disk1.raw,if=none,id=drive-data-disk1,media=disk,format=raw,cache=none -device ide-hd,drive=drive-data-disk1,id=data-disk1,unit=0 -drive file=/home/my-data-disk2.raw,if=none,id=drive-data-disk2,media=disk,format=raw,cache=none -device ide-hd,drive=drive-data-disk2,id=data-disk2,unit=1
(qemu) info qtree
...
      dev: ich9-ahci, id ""
        addr = 1f.2
        romfile = <null>
        rombar = 1
        multifunction = on
        command_serr_enable = on
        class SATA controller, addr 00:1f.2, pci id 8086:2922 (sub 1af4:1100)
        bar 4: i/o at 0xc140 [0xc15f]
        bar 5: mem at 0xfebf4000 [0xfebf4fff]
        bus: ide.5
          type IDE
          dev: ide-hd, id "data-disk2"
            drive = drive-data-disk2
            logical_block_size = 512
            physical_block_size = 512
            min_io_size = 0
            opt_io_size = 0
            bootindex = -1
            discard_granularity = 0
            ver = "1.4.0"
            wwn = 0x0
            serial = "QM00012"
            model = <null>
            cyls = 16383
            heads = 16
            secs = 63
            bios-chs-trans = lba
            unit = 1
          dev: ide-hd, id "data-disk1"
            drive = drive-data-disk1
            logical_block_size = 512
            physical_block_size = 512
            min_io_size = 0
            opt_io_size = 0
            bootindex = -1
            discard_granularity = 0
            ver = "1.4.0"
            wwn = 0x0
            serial = "QM00011"
            model = <null>
            cyls = 16383
            heads = 16
            secs = 63
            bios-chs-trans = lba
            unit = 0
        bus: ide.4
          type IDE
        bus: ide.3
          type IDE
        bus: ide.2
          type IDE
        bus: ide.1
          type IDE
        bus: ide.0
          type IDE
...

Result:
Press F12 for boot menu.

Select boot device:

1. AHCI/5 QEMU HARDDISK ATA-7 Hard-Disk (1024 MiBytes)
2. virtio-scsi Drive QEMU HARDDISK 1.4.
3. Legacy option rom
4. Floppy [drive A]
5. iPXE (PCI 00:05.0)

*** Bug 927138 has been marked as a duplicate of this bug. ***

AHCI has no concept of master/slave devices.  So attaching two ide devices to one (ahci) ide bus isn't going to work.  Try this instead:

  -device ide-{cd,hd},drive=${name},bus=ide.{0,1,2,3,4,5}

The emulated AHCI controller has 6 ports, each gets one ide bus, and this way you can attach up to 6 ide devices.

Due to ahci emulation sharing code with ide emulation and some nasty command line compatibility issues it is possible to create invalid configurations like you did.  Assigning to blockdev guys for investigation / status update (not sure whenever this has been addressed in 1.5 already).

Fixed upstream in commit 0ee20e66.

Build in qemu-kvm-1.5.0-1.el7

(In reply to Gerd Hoffmann from comment #6)
> AHCI has no concept of master/slave devices.  So attaching two ide devices
> to one (ahci) ide bus isn't going to work.  Try this instead:
> 
>   -device ide-{cd,hd},drive=${name},bus=ide.{0,1,2,3,4,5}
> 
> The emulated AHCI controller has 6 ports, each gets one ide bus, and this
> way you can attach up to 6 ide devices.
> 
> Due to ahci emulation sharing code with ide emulation and some nasty command
> line compatibility issues it is possible to create invalid configurations
> like you did.  Assigning to blockdev guys for investigation / status update
> (not sure whenever this has been addressed in 1.5 already).
ok, thanks for your information that AHCI has no concept of master/slave devices, I will make a note to our wiki.

Verify this issue on qemu-kvm-1.5.1-2.el7.x86_64.
host info:
3.10.0-0.rc7.64.el7.x86_64
qemu-kvm-1.5.1-2.el7.x86_64
guest info:
3.10.0-0.rc7.64.el7.x86_64

Steps and result:
1.the emulated AHCI controller has 6 ports, each gets one ide bus, and this way you can attach up to 6 ide devices, it work correctly.
e.g:/usr/libexec/qemu-kvm -S -M q35...-drive file=/home/en_windows_7_ultimate_with_sp1_x64_dvd_618240.iso,if=none,id=drive-cd-disk1,media=cdrom,format=raw,cache=none -device ide-cd,drive=drive-cd-disk1,id=cd-disk1,bus=ide.0,unit=0 -drive file=/home/en_windows_server_2012_x64_dvd_915478.iso,if=none,id=drive-cd-disk2,media=cdrom,format=raw,cache=none -device ide-cd,drive=drive-cd-disk2,id=cd-disk2,bus=ide.1,unit=0

1. Virtio disk PCI:3:0
2. Virtio disk PCI:a:0
3. Legacy option rom
4. Floppy [drive A]
5. DVD/CD [AHCI/0: QEMU DVD-ROM ATAPI-4 DVD/CD]
6. DVD/CD [AHCI/1: QEMU DVD-ROM ATAPI-4 DVD/CD]
7. iPXE (PCI 07:00.0)

2.Tried to create ide unit 1 for AHCI that qemu will fail to boot and give prompt that can't create IDE unit 1, bus supports only 1 units.
e.g:/usr/libexec/qemu-kvm -S -M q35...-drive file=/home/en_windows_7_ultimate_with_sp1_x64_dvd_618240.iso,if=none,id=drive-cd-disk1,media=cdrom,format=raw,cache=none -device ide-cd,drive=drive-cd-disk1,id=cd-disk1,bus=ide.0,unit=0 -drive file=/home/en_windows_server_2012_x64_dvd_915478.iso,if=none,id=drive-cd-disk2,media=cdrom,format=raw,cache=none -device ide-cd,drive=drive-cd-disk2,id=cd-disk2,bus=ide.0,unit=1
(qemu) qemu-kvm: -device ide-cd,drive=drive-cd-disk2,id=cd-disk2,bus=ide.0,unit=1: Can't create IDE unit 1, bus supports only 1 units
qemu-kvm: -device ide-cd,drive=drive-cd-disk2,id=cd-disk2,bus=ide.0,unit=1: Device initialization failed.
qemu-kvm: -device ide-cd,drive=drive-cd-disk2,id=cd-disk2,bus=ide.0,unit=1: Device 'ide-cd' could not be initialized
/etc/qemu-ifdown: could not launch network script


Base on above, this issue has been fixed correctly, set it to verified status.

Best Regards,
sluo

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.