Откат на предыдущую версию помогает. На ipxe-roms-qemu-20160525-alt1.gitf42b258 kvm падает с такой диагностикой: $ kvm -net nic,model=rtl8139 -net tap,ifname=qbox8,script=no -boot n qemu-system-x86_64: -net tap,ifname=qbox8,script=no: could not open /dev/net/tun: Permission denied [rider@hpc1 ~]$ sudo kvm -net nic,model=rtl8139 -net tap,ifname=qbox8,script=no -boot n KVM internal error. Suberror: 1 emulation failure EAX=f81c8cc0 EBX=000000a0 ECX=00002e50 EDX=0009f078 ESI=07fa4d90 EDI=07ed4000 EBP=ffffffff ESP=00007b92 EIP=000006ab EFL=00000087 [--S--PC] CPL=0 II=0 A20=1 SMM=0 HLT=0 ES =0000 00000000 ffffffff 00c09300 CS =9c48 0009c480 ffffffff 00809b00 SS =0000 00000000 ffffffff 00809300 DS =9ccc 0009ccc0 ffffffff 00c09300 FS =0000 00000000 ffffffff 00c09300 GS =0000 00000000 ffffffff 00c09300 LDT=0000 00000000 0000ffff 00008200 TR =0000 00000000 0000ffff 00008b00 GDT= 00000000 00000000 IDT= 00000000 000003ff CR0=00000010 CR2=00000000 CR3=00000000 CR4=00000000 DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 DR6=00000000ffff0ff0 DR7=0000000000000400 EFER=0000000000000000 Code=00 16 66 9c 66 60 0f a8 0f a0 06 1e 16 0e fa 2e 8e 1e 90 06 <0f> ae 06 00 1d 0f 01 0e f6 1c 0f 01 06 f0 1c fc 66 b9 38 00 00 00 66 ba 10 02 00 00 66 68
исправлено в 20150821-alt1.git4e03af8