The q35 machine uses AHCImounts cdrom under ich9-ahci instead of PIIX for cdrompiix3-ide, but I did not enable the SATA_AHCI. Enabling it solves the problem:
[ 0.568610] ata1: SATA link down (SStatus 0 SControl 300) [ 0.572271] ata4: SATA link down (SStatus 0 SControl 300) [ 0.572643] ata2: SATA link down (SStatus 0 SControl 300) [ 0.572997] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300) [ 0.573386] ata3.00: LPM support broken, forcing max_power [ 0.573688] ata3.00: ATAPI: QEMU DVD-ROM, 2.5+, max UDMA/100 [ 0.573997] ata3.00: applying bridge limits [ 0.574265] ata3.00: LPM support broken, forcing max_power [ 0.574565] ata3.00: configured for UDMA/100 [ 0.574894] scsi 2:0:0:0: CD-ROM QEMU QEMU DVD-ROM 2.5+ PQ: 0 ANSI: 5 [ 0.575549] sr 2:0:0:0: [sr0] scsi3-mmc drive: 4x/4x cd/rw xa/form2 tray [ 0.575909] cdrom: Uniform CD-ROM driver Revision: 3.20 [ 0.576416] ata6: SATA link down (SStatus 0 SControl 300) [ 0.576753] ata5: SATA link down (SStatus 0 SControl 300)