10 config LOCKDEP_SUPPORT
13 config STACKTRACE_SUPPORT
16 config RWSEM_GENERIC_SPINLOCK
19 config RWSEM_XCHGADD_ALGORITHM
22 config ARCH_HAS_ILOG2_U32
25 config ARCH_HAS_ILOG2_U64
28 config GENERIC_HWEIGHT
34 config GENERIC_BUG_RELATIVE_POINTERS
37 config ARCH_DMA_ADDR_T_64BIT
40 config GENERIC_LOCKBREAK
41 def_bool y if SMP && PREEMPT
46 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
62 config ARCH_SUPPORTS_UPROBES
67 select ARCH_BINFMT_ELF_STATE
68 select ARCH_HAS_DEVMEM_IS_ALLOWED
69 select ARCH_HAS_ELF_RANDOMIZE
70 select ARCH_HAS_GCOV_PROFILE_ALL
71 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
73 select ARCH_HAS_SET_MEMORY
74 select ARCH_HAS_SG_CHAIN
75 select ARCH_HAS_STRICT_KERNEL_RWX
76 select ARCH_HAS_STRICT_MODULE_RWX
77 select ARCH_HAS_UBSAN_SANITIZE_ALL
78 select ARCH_HAVE_NMI_SAFE_CMPXCHG
79 select ARCH_INLINE_READ_LOCK
80 select ARCH_INLINE_READ_LOCK_BH
81 select ARCH_INLINE_READ_LOCK_IRQ
82 select ARCH_INLINE_READ_LOCK_IRQSAVE
83 select ARCH_INLINE_READ_TRYLOCK
84 select ARCH_INLINE_READ_UNLOCK
85 select ARCH_INLINE_READ_UNLOCK_BH
86 select ARCH_INLINE_READ_UNLOCK_IRQ
87 select ARCH_INLINE_READ_UNLOCK_IRQRESTORE
88 select ARCH_INLINE_SPIN_LOCK
89 select ARCH_INLINE_SPIN_LOCK_BH
90 select ARCH_INLINE_SPIN_LOCK_IRQ
91 select ARCH_INLINE_SPIN_LOCK_IRQSAVE
92 select ARCH_INLINE_SPIN_TRYLOCK
93 select ARCH_INLINE_SPIN_TRYLOCK_BH
94 select ARCH_INLINE_SPIN_UNLOCK
95 select ARCH_INLINE_SPIN_UNLOCK_BH
96 select ARCH_INLINE_SPIN_UNLOCK_IRQ
97 select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE
98 select ARCH_INLINE_WRITE_LOCK
99 select ARCH_INLINE_WRITE_LOCK_BH
100 select ARCH_INLINE_WRITE_LOCK_IRQ
101 select ARCH_INLINE_WRITE_LOCK_IRQSAVE
102 select ARCH_INLINE_WRITE_TRYLOCK
103 select ARCH_INLINE_WRITE_UNLOCK
104 select ARCH_INLINE_WRITE_UNLOCK_BH
105 select ARCH_INLINE_WRITE_UNLOCK_IRQ
106 select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
107 select ARCH_SAVE_PAGE_KEYS if HIBERNATION
108 select ARCH_SUPPORTS_ATOMIC_RMW
109 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
110 select ARCH_SUPPORTS_NUMA_BALANCING
111 select ARCH_USE_BUILTIN_BSWAP
112 select ARCH_USE_CMPXCHG_LOCKREF
113 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
114 select ARCH_WANTS_PROT_NUMA_PROT_NONE
115 select ARCH_WANTS_UBSAN_NO_NULL
116 select ARCH_WANT_IPC_PARSE_VERSION
117 select BUILDTIME_EXTABLE_SORT
118 select CLONE_BACKWARDS2
119 select DYNAMIC_FTRACE if FUNCTION_TRACER
120 select GENERIC_CLOCKEVENTS
121 select GENERIC_CPU_AUTOPROBE
122 select GENERIC_CPU_DEVICES if !SMP
123 select GENERIC_FIND_FIRST_BIT
124 select GENERIC_SMP_IDLE_THREAD
125 select GENERIC_TIME_VSYSCALL
126 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
127 select HAVE_ARCH_AUDITSYSCALL
128 select HAVE_ARCH_JUMP_LABEL
129 select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES
130 select HAVE_ARCH_SECCOMP_FILTER
131 select HAVE_ARCH_SOFT_DIRTY
132 select HAVE_ARCH_TRACEHOOK
133 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
134 select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
135 select HAVE_CMPXCHG_DOUBLE
136 select HAVE_CMPXCHG_LOCAL
137 select HAVE_COPY_THREAD_TLS
138 select HAVE_DEBUG_KMEMLEAK
139 select HAVE_DMA_API_DEBUG
140 select HAVE_DMA_CONTIGUOUS
142 select HAVE_DYNAMIC_FTRACE
143 select HAVE_DYNAMIC_FTRACE_WITH_REGS
144 select HAVE_EFFICIENT_UNALIGNED_ACCESS
145 select HAVE_EXIT_THREAD
146 select HAVE_FTRACE_MCOUNT_RECORD
147 select HAVE_FUNCTION_GRAPH_TRACER
148 select HAVE_FUNCTION_TRACER
149 select HAVE_FUTEX_CMPXCHG if FUTEX
150 select HAVE_KERNEL_BZIP2
151 select HAVE_KERNEL_GZIP
152 select HAVE_KERNEL_LZ4
153 select HAVE_KERNEL_LZMA
154 select HAVE_KERNEL_LZO
155 select HAVE_KERNEL_XZ
157 select HAVE_KRETPROBES
159 select HAVE_LIVEPATCH
161 select HAVE_MEMBLOCK_NODE_MAP
162 select HAVE_MEMBLOCK_PHYS_MAP
163 select HAVE_MOD_ARCH_SPECIFIC
165 select HAVE_PERF_EVENTS
166 select HAVE_REGS_AND_STACK_ACCESS_API
167 select HAVE_SYSCALL_TRACEPOINTS
168 select HAVE_VIRT_CPU_ACCOUNTING
169 select MODULES_USE_ELF_RELA
172 select OLD_SIGSUSPEND3
174 select SYSCTL_EXCEPTION_TRACE
175 select THREAD_INFO_IN_TASK
177 select VIRT_CPU_ACCOUNTING
178 select ARCH_HAS_SCALED_CPUTIME
183 config SCHED_OMIT_FRAME_POINTER
186 config PGTABLE_LEVELS
190 source "init/Kconfig"
192 source "kernel/Kconfig.freezer"
194 source "kernel/livepatch/Kconfig"
196 menu "Processor type and features"
198 config HAVE_MARCH_Z900_FEATURES
201 config HAVE_MARCH_Z990_FEATURES
203 select HAVE_MARCH_Z900_FEATURES
205 config HAVE_MARCH_Z9_109_FEATURES
207 select HAVE_MARCH_Z990_FEATURES
209 config HAVE_MARCH_Z10_FEATURES
211 select HAVE_MARCH_Z9_109_FEATURES
213 config HAVE_MARCH_Z196_FEATURES
215 select HAVE_MARCH_Z10_FEATURES
217 config HAVE_MARCH_ZEC12_FEATURES
219 select HAVE_MARCH_Z196_FEATURES
221 config HAVE_MARCH_Z13_FEATURES
223 select HAVE_MARCH_ZEC12_FEATURES
225 config HAVE_MARCH_Z14_FEATURES
227 select HAVE_MARCH_Z13_FEATURES
230 prompt "Processor type"
234 bool "IBM zSeries model z800 and z900"
235 select HAVE_MARCH_Z900_FEATURES
237 Select this to enable optimizations for model z800/z900 (2064 and
238 2066 series). This will enable some optimizations that are not
239 available on older ESA/390 (31 Bit) only CPUs.
242 bool "IBM zSeries model z890 and z990"
243 select HAVE_MARCH_Z990_FEATURES
245 Select this to enable optimizations for model z890/z990 (2084 and
246 2086 series). The kernel will be slightly faster but will not work
251 select HAVE_MARCH_Z9_109_FEATURES
253 Select this to enable optimizations for IBM System z9 (2094 and
254 2096 series). The kernel will be slightly faster but will not work
258 bool "IBM System z10"
259 select HAVE_MARCH_Z10_FEATURES
261 Select this to enable optimizations for IBM System z10 (2097 and
262 2098 series). The kernel will be slightly faster but will not work
266 bool "IBM zEnterprise 114 and 196"
267 select HAVE_MARCH_Z196_FEATURES
269 Select this to enable optimizations for IBM zEnterprise 114 and 196
270 (2818 and 2817 series). The kernel will be slightly faster but will
271 not work on older machines.
274 bool "IBM zBC12 and zEC12"
275 select HAVE_MARCH_ZEC12_FEATURES
277 Select this to enable optimizations for IBM zBC12 and zEC12 (2828 and
278 2827 series). The kernel will be slightly faster but will not work on
282 bool "IBM z13s and z13"
283 select HAVE_MARCH_Z13_FEATURES
285 Select this to enable optimizations for IBM z13s and z13 (2965 and
286 2964 series). The kernel will be slightly faster but will not work on
291 select HAVE_MARCH_Z14_FEATURES
293 Select this to enable optimizations for IBM z14 (3906 series).
294 The kernel will be slightly faster but will not work on older
299 config MARCH_Z900_TUNE
300 def_bool TUNE_Z900 || MARCH_Z900 && TUNE_DEFAULT
302 config MARCH_Z990_TUNE
303 def_bool TUNE_Z990 || MARCH_Z990 && TUNE_DEFAULT
305 config MARCH_Z9_109_TUNE
306 def_bool TUNE_Z9_109 || MARCH_Z9_109 && TUNE_DEFAULT
308 config MARCH_Z10_TUNE
309 def_bool TUNE_Z10 || MARCH_Z10 && TUNE_DEFAULT
311 config MARCH_Z196_TUNE
312 def_bool TUNE_Z196 || MARCH_Z196 && TUNE_DEFAULT
314 config MARCH_ZEC12_TUNE
315 def_bool TUNE_ZEC12 || MARCH_ZEC12 && TUNE_DEFAULT
317 config MARCH_Z13_TUNE
318 def_bool TUNE_Z13 || MARCH_Z13 && TUNE_DEFAULT
320 config MARCH_Z14_TUNE
321 def_bool TUNE_Z14 || MARCH_Z14 && TUNE_DEFAULT
324 prompt "Tune code generation"
327 Cause the compiler to tune (-mtune) the generated code for a machine.
328 This will make the code run faster on the selected machine but
329 somewhat slower on other machines.
330 This option only changes how the compiler emits instructions, not the
331 selection of instructions itself, so the resulting kernel will run on
337 Tune the generated code for the target processor for which the kernel
341 bool "IBM zSeries model z800 and z900"
344 bool "IBM zSeries model z890 and z990"
350 bool "IBM System z10"
353 bool "IBM zEnterprise 114 and 196"
356 bool "IBM zBC12 and zEC12"
371 prompt "Kernel support for 31 bit emulation"
372 select COMPAT_BINFMT_ELF if BINFMT_ELF
373 select ARCH_WANT_OLD_COMPAT_IPC
374 select COMPAT_OLD_SIGACTION
377 Select this option if you want to enable your system kernel to
378 handle system-calls from ELF binaries for 31 bit ESA. This option
379 (and some other stuff like libraries and such) is needed for
380 executing 31 bit applications. It is safe to say "Y".
382 config SYSVIPC_COMPAT
383 def_bool y if COMPAT && SYSVIPC
387 prompt "Symmetric multi-processing support"
389 This enables support for systems with more than one CPU. If you have
390 a system with only one CPU, like most personal computers, say N. If
391 you have a system with more than one CPU, say Y.
393 If you say N here, the kernel will run on uni- and multiprocessor
394 machines, but will use only one CPU of a multiprocessor machine. If
395 you say Y here, the kernel will run on many, but not all,
396 uniprocessor machines. On a uniprocessor machine, the kernel
397 will run faster if you say N here.
399 See also the SMP-HOWTO available at
400 <http://www.tldp.org/docs.html#howto>.
402 Even if you don't know what to do here, say Y.
405 int "Maximum number of CPUs (2-512)"
410 This allows you to specify the maximum number of CPUs which this
411 kernel will support. The maximum supported value is 512 and the
412 minimum value which makes sense is 2.
414 This is purely to save memory - each supported CPU adds
415 approximately sixteen kilobytes to the kernel image.
419 prompt "Support for hot-pluggable CPUs"
422 Say Y here to be able to turn CPUs off and on. CPUs
423 can be controlled through /sys/devices/system/cpu/cpu#.
424 Say N if you want to disable CPU hotplug.
426 # Some NUMA nodes have memory ranges that span
427 # other nodes. Even though a pfn is valid and
428 # between a node's start and end pfns, it may not
429 # reside on that node. See memmap_init_zone()
430 # for details. <- They meant memory holes!
431 config NODES_SPAN_OTHER_NODES
436 depends on SMP && SCHED_TOPOLOGY
441 This option adds NUMA support to the kernel.
443 An operation mode can be selected by appending
444 numa=<method> to the kernel command line.
446 The default behaviour is identical to appending numa=plain to
447 the command line. This will create just one node with all
448 available memory and all CPUs in it.
451 int "Maximum NUMA nodes (as a power of 2)"
456 Specify the maximum number of NUMA nodes available on the target
457 system. Increases memory reserved to accommodate various tables.
459 menu "Select NUMA modes"
463 bool "NUMA emulation"
466 Numa emulation mode will split the available system memory into
467 equal chunks which then are distributed over the configured number
468 of nodes in a round-robin manner.
470 The number of fake nodes is limited by the number of available memory
471 chunks (i.e. memory size / fake size) and the number of supported
474 The CPUs are assigned to the nodes in a way that partially respects
475 the original machine topology (if supported by the machine).
476 Fair distribution of the CPUs is not guaranteed.
479 hex "NUMA emulation memory chunk size"
481 range 0x400000 0x100000000
484 Select the default size by which the memory is chopped and then
485 assigned to emulated NUMA nodes.
487 This can be overridden by specifying
491 on the kernel command line where also suffixes K, M, G, and T are
508 config SCHED_TOPOLOGY
510 prompt "Topology scheduler support"
517 Topology scheduler support improves the CPU scheduler's decision
518 making when dealing with machines that have multi-threading,
519 multiple cores or multiple books.
521 source kernel/Kconfig.preempt
523 source kernel/Kconfig.hz
527 prompt "s390 architectural random number generation API"
529 Enable the s390 architectural random number generation API
530 to provide random data for all consumers within the Linux
533 When enabled the arch_random_* functions declared in linux/random.h
534 are implemented. The implementation is based on the s390 CPACF
535 instruction subfunction TRNG which provides a real true random
544 config ARCH_SPARSEMEM_ENABLE
546 select SPARSEMEM_VMEMMAP_ENABLE
547 select SPARSEMEM_VMEMMAP
549 config ARCH_SPARSEMEM_DEFAULT
552 config ARCH_SELECT_MEMORY_MODEL
555 config ARCH_ENABLE_MEMORY_HOTPLUG
556 def_bool y if SPARSEMEM
558 config ARCH_ENABLE_MEMORY_HOTREMOVE
561 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
564 config FORCE_MAX_ZONEORDER
570 config MAX_PHYSMEM_BITS
571 int "Maximum size of supported physical memory in bits (42-53)"
575 This option specifies the maximum supported size of physical memory
576 in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB).
577 Increasing the number of bits also increases the kernel image size.
578 By default 46 bits (64TB) are supported.
582 prompt "Pack kernel stack"
584 This option enables the compiler option -mkernel-backchain if it
585 is available. If the option is available the compiler supports
586 the new stack layout which dramatically reduces the minimum stack
587 frame size. With an old compiler a non-leaf function needs a
588 minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
589 -mkernel-backchain the minimum size drops to 16 byte on 31 bit
590 and 24 byte on 64 bit.
592 Say Y if you are unsure.
596 prompt "Detect kernel stack overflow"
598 This option enables the compiler option -mstack-guard and
599 -mstack-size if they are available. If the compiler supports them
600 it will emit additional code to each function prolog to trigger
601 an illegal operation if the kernel stack is about to overflow.
603 Say N if you are unsure.
606 int "Size of the guard area (128-1024)"
608 depends on CHECK_STACK
611 This allows you to specify the size of the guard area at the lower
612 end of the kernel stack. If the kernel stack points into the guard
613 area on function entry an illegal operation is triggered. The size
614 needs to be a power of 2. Please keep in mind that the size of an
615 interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
616 The minimum size for the stack guard should be 256 for 31 bit and
619 config WARN_DYNAMIC_STACK
621 prompt "Emit compiler warnings for function with dynamic stack usage"
623 This option enables the compiler option -mwarn-dynamicstack. If the
624 compiler supports this options generates warnings for functions
625 that dynamically allocate stack space using alloca.
627 Say N if you are unsure.
635 prompt "QDIO support"
637 This driver provides the Queued Direct I/O base support for
640 To compile this driver as a module, choose M here: the
641 module will be called qdio.
654 config PCI_NR_FUNCTIONS
655 int "Maximum number of PCI functions (1-4096)"
659 This allows you to specify the maximum number of PCI functions which
660 this kernel will support.
662 source "drivers/pci/Kconfig"
675 config NEED_SG_DMA_LENGTH
678 config NEED_DMA_MAP_STATE
683 prompt "Support for CHSC subchannels"
685 This driver allows usage of CHSC subchannels. A CHSC subchannel
686 is usually present on LPAR only.
687 The driver creates a device /dev/chsc, which may be used to
688 obtain I/O configuration information about the machine and
689 to issue asynchronous chsc commands (DANGEROUS).
690 You will usually only want to use this interface on a special
691 LPAR designated for system management.
693 To compile this driver as a module, choose M here: the
694 module will be called chsc_sch.
700 prompt "SCM bus driver"
702 Bus driver for Storage Class Memory.
706 prompt "Support for EADM subchannels"
709 This driver allows usage of EADM subchannels. EADM subchannels act
710 as a communication vehicle for SCM increments.
712 To compile this driver as a module, choose M here: the
713 module will be called eadm_sch.
717 prompt "Support for VFIO-CCW subchannels"
718 depends on S390_CCW_IOMMU && VFIO_MDEV
720 This driver allows usage of I/O subchannels via VFIO-CCW.
722 To compile this driver as a module, choose M here: the
723 module will be called vfio_ccw.
730 bool "kernel crash dumps"
734 Generate crash dump after being started by kexec.
735 Crash dump kernels are loaded in the main kernel with kexec-tools
736 into a specially reserved region and then later executed after
737 a crash by kdump/kexec.
738 Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
739 This option also enables s390 zfcpdump.
740 See also <file:Documentation/s390/zfcpdump.txt>
744 menu "Executable file formats / Emulations"
746 source "fs/Kconfig.binfmt"
750 prompt "Enable seccomp to safely compute untrusted bytecode"
753 This kernel feature is useful for number crunching applications
754 that may need to compute untrusted bytecode during their
755 execution. By using pipes or other transports made available to
756 the process as file descriptors supporting the read/write
757 syscalls, it's possible to isolate those applications in
758 their own address space using seccomp. Once seccomp is
759 enabled via /proc/<pid>/seccomp, it cannot be disabled
760 and the task is only allowed to execute a few safe syscalls
761 defined by each seccomp mode.
767 menu "Power Management"
769 config ARCH_HIBERNATION_POSSIBLE
772 source "kernel/power/Kconfig"
784 source "drivers/Kconfig"
788 source "arch/s390/Kconfig.debug"
790 source "security/Kconfig"
792 source "crypto/Kconfig"
796 menu "Virtualization"
800 prompt "Pseudo page fault support"
802 Select this option, if you want to use PFAULT pseudo page fault
803 handling under VM. If running native or in LPAR, this option
804 has no effect. If your VM does not support PFAULT, PAGEEX
805 pseudo page fault handling will be used.
806 Note that VM 4.2 supports PFAULT but has a bug in its
807 implementation that causes some problems.
808 Everybody who wants to run Linux under VM != VM4.2 should select
812 bool "VM shared kernel support"
813 depends on !JUMP_LABEL
815 Select this option, if you want to share the text segment of the
816 Linux kernel between different VM guests. This reduces memory
817 usage with lots of guests but greatly increases kernel size.
818 Also if a kernel was IPL'ed from a shared segment the kexec system
820 You should only select this option if you know what you are
821 doing and want to exploit this feature.
825 prompt "Cooperative memory management"
827 Select this option, if you want to enable the kernel interface
828 to reduce the memory size of the system. This is accomplished
829 by allocating pages of memory and put them "on hold". This only
830 makes sense for a system running under VM where the unused pages
831 will be reused by VM for other guest systems. The interface
832 allows an external monitor to balance memory of many systems.
833 Everybody who wants to run Linux under VM should select this
838 prompt "IUCV special message interface to cooperative memory management"
839 depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
841 Select this option to enable the special message interface to
842 the cooperative memory management.
846 prompt "Linux - VM Monitor Stream, base infrastructure"
849 This provides a kernel interface for creating and updating z/VM APPLDATA
850 monitor records. The monitor records are updated at certain time
851 intervals, once the timer is started.
852 Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
853 i.e. enables or disables monitoring on the Linux side.
854 A custom interval value (in seconds) can be written to
855 /proc/appldata/interval.
857 Defaults are 60 seconds interval and timer off.
858 The /proc entries can also be read from, showing the current settings.
862 prompt "Monitor memory management statistics"
863 depends on APPLDATA_BASE && VM_EVENT_COUNTERS
865 This provides memory management related data to the Linux - VM Monitor
866 Stream, like paging/swapping rate, memory utilisation, etc.
867 Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
868 APPLDATA monitor record, i.e. enables or disables monitoring this record
872 The /proc entry can also be read from, showing the current settings.
874 This can also be compiled as a module, which will be called
879 prompt "Monitor OS statistics"
880 depends on APPLDATA_BASE
882 This provides OS related data to the Linux - VM Monitor Stream, like
883 CPU utilisation, etc.
884 Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
885 APPLDATA monitor record, i.e. enables or disables monitoring this record
889 This can also be compiled as a module, which will be called
892 config APPLDATA_NET_SUM
894 prompt "Monitor overall network statistics"
895 depends on APPLDATA_BASE && NET
897 This provides network related data to the Linux - VM Monitor Stream,
898 currently there is only a total sum of network I/O statistics, no
900 Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
901 APPLDATA monitor record, i.e. enables or disables monitoring this record
905 This can also be compiled as a module, which will be called
910 prompt "s390 hypervisor file system support"
911 select SYS_HYPERVISOR
913 This is a virtual file system intended to provide accounting
914 information in an s390 hypervisor environment.
916 source "arch/s390/kvm/Kconfig"
920 prompt "s390 support for virtio devices"
922 select VIRTUALIZATION
924 select VIRTIO_CONSOLE
926 Enabling this option adds support for virtio based paravirtual device
929 Select this option if you want to run the kernel as a guest under
932 config S390_GUEST_OLD_TRANSPORT
934 prompt "Guest support for old s390 virtio transport (DEPRECATED)"
935 depends on S390_GUEST
937 Enable this option to add support for the old s390-virtio
938 transport (i.e. virtio devices NOT based on virtio-ccw). This
939 type of virtio devices is only available on the experimental
940 kuli userspace or with old (< 2.6) qemu. If you are running
941 with a modern version of qemu (which supports virtio-ccw since
942 1.4 and uses it by default since version 2.4), you probably won't