arch/s390/Kconfig

   1 config MMU
   2         def_bool y
   3
   4 config ZONE_DMA
   5         def_bool y
   6
   7 config LOCKDEP_SUPPORT
   8         def_bool y
   9
  10 config STACKTRACE_SUPPORT
  11         def_bool y
  12
  13 config HAVE_LATENCYTOP_SUPPORT
  14         def_bool y
  15
  16 config RWSEM_GENERIC_SPINLOCK
  17         bool
  18
  19 config RWSEM_XCHGADD_ALGORITHM
  20         def_bool y
  21
  22 config ARCH_HAS_ILOG2_U32
  23         def_bool n
  24
  25 config ARCH_HAS_ILOG2_U64
  26         def_bool n
  27
  28 config GENERIC_HWEIGHT
  29         def_bool y
  30
  31 config GENERIC_BUG
  32         def_bool y if BUG
  33
  34 config GENERIC_BUG_RELATIVE_POINTERS
  35         def_bool y
  36
  37 config NO_IOMEM
  38         def_bool y
  39
  40 config NO_DMA
  41         def_bool y
  42
  43 config ARCH_DMA_ADDR_T_64BIT
  44         def_bool 64BIT
  45
  46 config GENERIC_LOCKBREAK
  47         def_bool y if SMP && PREEMPT
  48
  49 config PGSTE
  50         def_bool y if KVM
  51
  52 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
  53         def_bool y
  54
  55 config KEXEC
  56         def_bool y
  57
  58 config AUDIT_ARCH
  59         def_bool y
  60
  61 config S390
  62         def_bool y
  63         select USE_GENERIC_SMP_HELPERS if SMP
  64         select GENERIC_CPU_DEVICES if !SMP
  65         select HAVE_SYSCALL_WRAPPERS
  66         select HAVE_FUNCTION_TRACER
  67         select HAVE_FUNCTION_TRACE_MCOUNT_TEST
  68         select HAVE_FTRACE_MCOUNT_RECORD
  69         select HAVE_C_RECORDMCOUNT
  70         select HAVE_SYSCALL_TRACEPOINTS
  71         select SYSCTL_EXCEPTION_TRACE
  72         select HAVE_DYNAMIC_FTRACE
  73         select HAVE_FUNCTION_GRAPH_TRACER
  74         select HAVE_REGS_AND_STACK_ACCESS_API
  75         select HAVE_OPROFILE
  76         select HAVE_KPROBES
  77         select HAVE_KRETPROBES
  78         select HAVE_KVM if 64BIT
  79         select HAVE_ARCH_TRACEHOOK
  80         select INIT_ALL_POSSIBLE
  81         select HAVE_IRQ_WORK
  82         select HAVE_PERF_EVENTS
  83         select ARCH_HAVE_NMI_SAFE_CMPXCHG
  84         select HAVE_DEBUG_KMEMLEAK
  85         select HAVE_KERNEL_GZIP
  86         select HAVE_KERNEL_BZIP2
  87         select HAVE_KERNEL_LZMA
  88         select HAVE_KERNEL_LZO
  89         select HAVE_KERNEL_XZ
  90         select HAVE_ARCH_MUTEX_CPU_RELAX
  91         select HAVE_ARCH_JUMP_LABEL if !MARCH_G5
  92         select HAVE_BPF_JIT if 64BIT && PACK_STACK
  93         select ARCH_SAVE_PAGE_KEYS if HIBERNATION
  94         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
  95         select HAVE_MEMBLOCK
  96         select HAVE_MEMBLOCK_NODE_MAP
  97         select HAVE_CMPXCHG_LOCAL
  98         select HAVE_CMPXCHG_DOUBLE
  99         select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 100         select HAVE_VIRT_CPU_ACCOUNTING
 101         select VIRT_CPU_ACCOUNTING
 102         select ARCH_DISCARD_MEMBLOCK
 103         select BUILDTIME_EXTABLE_SORT
 104         select ARCH_INLINE_SPIN_TRYLOCK
 105         select ARCH_INLINE_SPIN_TRYLOCK_BH
 106         select ARCH_INLINE_SPIN_LOCK
 107         select ARCH_INLINE_SPIN_LOCK_BH
 108         select ARCH_INLINE_SPIN_LOCK_IRQ
 109         select ARCH_INLINE_SPIN_LOCK_IRQSAVE
 110         select ARCH_INLINE_SPIN_UNLOCK
 111         select ARCH_INLINE_SPIN_UNLOCK_BH
 112         select ARCH_INLINE_SPIN_UNLOCK_IRQ
 113         select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE
 114         select ARCH_INLINE_READ_TRYLOCK
 115         select ARCH_INLINE_READ_LOCK
 116         select ARCH_INLINE_READ_LOCK_BH
 117         select ARCH_INLINE_READ_LOCK_IRQ
 118         select ARCH_INLINE_READ_LOCK_IRQSAVE
 119         select ARCH_INLINE_READ_UNLOCK
 120         select ARCH_INLINE_READ_UNLOCK_BH
 121         select ARCH_INLINE_READ_UNLOCK_IRQ
 122         select ARCH_INLINE_READ_UNLOCK_IRQRESTORE
 123         select ARCH_INLINE_WRITE_TRYLOCK
 124         select ARCH_INLINE_WRITE_LOCK
 125         select ARCH_INLINE_WRITE_LOCK_BH
 126         select ARCH_INLINE_WRITE_LOCK_IRQ
 127         select ARCH_INLINE_WRITE_LOCK_IRQSAVE
 128         select ARCH_INLINE_WRITE_UNLOCK
 129         select ARCH_INLINE_WRITE_UNLOCK_BH
 130         select ARCH_INLINE_WRITE_UNLOCK_IRQ
 131         select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 132         select HAVE_UID16 if 32BIT
 133         select ARCH_WANT_IPC_PARSE_VERSION
 134         select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT
 135         select GENERIC_SMP_IDLE_THREAD
 136         select GENERIC_TIME_VSYSCALL_OLD
 137         select GENERIC_CLOCKEVENTS
 138         select KTIME_SCALAR if 32BIT
 139         select HAVE_ARCH_SECCOMP_FILTER
 140         select GENERIC_KERNEL_THREAD
 141         select HAVE_MOD_ARCH_SPECIFIC
 142         select MODULES_USE_ELF_RELA
 143
 144 config SCHED_OMIT_FRAME_POINTER
 145         def_bool y
 146
 147 source "init/Kconfig"
 148
 149 source "kernel/Kconfig.freezer"
 150
 151 menu "Processor type and features"
 152
 153 config HAVE_MARCH_Z900_FEATURES
 154         def_bool n
 155
 156 config HAVE_MARCH_Z990_FEATURES
 157         def_bool n
 158         select HAVE_MARCH_Z900_FEATURES
 159
 160 config HAVE_MARCH_Z9_109_FEATURES
 161         def_bool n
 162         select HAVE_MARCH_Z990_FEATURES
 163
 164 config HAVE_MARCH_Z10_FEATURES
 165         def_bool n
 166         select HAVE_MARCH_Z9_109_FEATURES
 167
 168 config HAVE_MARCH_Z196_FEATURES
 169         def_bool n
 170         select HAVE_MARCH_Z10_FEATURES
 171
 172 choice
 173         prompt "Processor type"
 174         default MARCH_G5
 175
 176 config MARCH_G5
 177         bool "System/390 model G5 and G6"
 178         depends on !64BIT
 179         help
 180           Select this to build a 31 bit kernel that works
 181           on all ESA/390 and z/Architecture machines.
 182
 183 config MARCH_Z900
 184         bool "IBM zSeries model z800 and z900"
 185         select HAVE_MARCH_Z900_FEATURES if 64BIT
 186         help
 187           Select this to enable optimizations for model z800/z900 (2064 and
 188           2066 series). This will enable some optimizations that are not
 189           available on older ESA/390 (31 Bit) only CPUs.
 190
 191 config MARCH_Z990
 192         bool "IBM zSeries model z890 and z990"
 193         select HAVE_MARCH_Z990_FEATURES if 64BIT
 194         help
 195           Select this to enable optimizations for model z890/z990 (2084 and
 196           2086 series). The kernel will be slightly faster but will not work
 197           on older machines.
 198
 199 config MARCH_Z9_109
 200         bool "IBM System z9"
 201         select HAVE_MARCH_Z9_109_FEATURES if 64BIT
 202         help
 203           Select this to enable optimizations for IBM System z9 (2094 and
 204           2096 series). The kernel will be slightly faster but will not work
 205           on older machines.
 206
 207 config MARCH_Z10
 208         bool "IBM System z10"
 209         select HAVE_MARCH_Z10_FEATURES if 64BIT
 210         help
 211           Select this to enable optimizations for IBM System z10 (2097 and
 212           2098 series). The kernel will be slightly faster but will not work
 213           on older machines.
 214
 215 config MARCH_Z196
 216         bool "IBM zEnterprise 114 and 196"
 217         select HAVE_MARCH_Z196_FEATURES if 64BIT
 218         help
 219           Select this to enable optimizations for IBM zEnterprise 114 and 196
 220           (2818 and 2817 series). The kernel will be slightly faster but will
 221           not work on older machines.
 222
 223 endchoice
 224
 225 config 64BIT
 226         def_bool y
 227         prompt "64 bit kernel"
 228         help
 229           Select this option if you have an IBM z/Architecture machine
 230           and want to use the 64 bit addressing mode.
 231
 232 config 32BIT
 233         def_bool y if !64BIT
 234
 235 config COMPAT
 236         def_bool y
 237         prompt "Kernel support for 31 bit emulation"
 238         depends on 64BIT
 239         select COMPAT_BINFMT_ELF if BINFMT_ELF
 240         select ARCH_WANT_OLD_COMPAT_IPC
 241         help
 242           Select this option if you want to enable your system kernel to
 243           handle system-calls from ELF binaries for 31 bit ESA.  This option
 244           (and some other stuff like libraries and such) is needed for
 245           executing 31 bit applications.  It is safe to say "Y".
 246
 247 config SYSVIPC_COMPAT
 248         def_bool y if COMPAT && SYSVIPC
 249
 250 config KEYS_COMPAT
 251         def_bool y if COMPAT && KEYS
 252
 253 config SMP
 254         def_bool y
 255         prompt "Symmetric multi-processing support"
 256         ---help---
 257           This enables support for systems with more than one CPU. If you have
 258           a system with only one CPU, like most personal computers, say N. If
 259           you have a system with more than one CPU, say Y.
 260
 261           If you say N here, the kernel will run on single and multiprocessor
 262           machines, but will use only one CPU of a multiprocessor machine. If
 263           you say Y here, the kernel will run on many, but not all,
 264           singleprocessor machines. On a singleprocessor machine, the kernel
 265           will run faster if you say N here.
 266
 267           See also the SMP-HOWTO available at
 268           <http://www.tldp.org/docs.html#howto>.
 269
 270           Even if you don't know what to do here, say Y.
 271
 272 config NR_CPUS
 273         int "Maximum number of CPUs (2-64)"
 274         range 2 64
 275         depends on SMP
 276         default "32" if !64BIT
 277         default "64" if 64BIT
 278         help
 279           This allows you to specify the maximum number of CPUs which this
 280           kernel will support.  The maximum supported value is 64 and the
 281           minimum value which makes sense is 2.
 282
 283           This is purely to save memory - each supported CPU adds
 284           approximately sixteen kilobytes to the kernel image.
 285
 286 config HOTPLUG_CPU
 287         def_bool y
 288         prompt "Support for hot-pluggable CPUs"
 289         depends on SMP
 290         select HOTPLUG
 291         help
 292           Say Y here to be able to turn CPUs off and on. CPUs
 293           can be controlled through /sys/devices/system/cpu/cpu#.
 294           Say N if you want to disable CPU hotplug.
 295
 296 config SCHED_MC
 297         def_bool n
 298
 299 config SCHED_BOOK
 300         def_bool y
 301         prompt "Book scheduler support"
 302         depends on SMP
 303         select SCHED_MC
 304         help
 305           Book scheduler support improves the CPU scheduler's decision making
 306           when dealing with machines that have several books.
 307
 308 source kernel/Kconfig.preempt
 309
 310 config MATHEMU
 311         def_bool y
 312         prompt "IEEE FPU emulation"
 313         depends on MARCH_G5
 314         help
 315           This option is required for IEEE compliant floating point arithmetic
 316           on older ESA/390 machines. Say Y unless you know your machine doesn't
 317           need this.
 318
 319 source kernel/Kconfig.hz
 320
 321 endmenu
 322
 323 menu "Memory setup"
 324
 325 config ARCH_SPARSEMEM_ENABLE
 326         def_bool y
 327         select SPARSEMEM_VMEMMAP_ENABLE
 328         select SPARSEMEM_VMEMMAP
 329         select SPARSEMEM_STATIC if !64BIT
 330
 331 config ARCH_SPARSEMEM_DEFAULT
 332         def_bool y
 333
 334 config ARCH_SELECT_MEMORY_MODEL
 335         def_bool y
 336
 337 config ARCH_ENABLE_MEMORY_HOTPLUG
 338         def_bool y if SPARSEMEM
 339
 340 config ARCH_ENABLE_MEMORY_HOTREMOVE
 341         def_bool y
 342
 343 config FORCE_MAX_ZONEORDER
 344         int
 345         default "9"
 346
 347 source "mm/Kconfig"
 348
 349 config PACK_STACK
 350         def_bool y
 351         prompt "Pack kernel stack"
 352         help
 353           This option enables the compiler option -mkernel-backchain if it
 354           is available. If the option is available the compiler supports
 355           the new stack layout which dramatically reduces the minimum stack
 356           frame size. With an old compiler a non-leaf function needs a
 357           minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
 358           -mkernel-backchain the minimum size drops to 16 byte on 31 bit
 359           and 24 byte on 64 bit.
 360
 361           Say Y if you are unsure.
 362
 363 config SMALL_STACK
 364         def_bool n
 365         prompt "Use 8kb for kernel stack instead of 16kb"
 366         depends on PACK_STACK && 64BIT && !LOCKDEP
 367         help
 368           If you say Y here and the compiler supports the -mkernel-backchain
 369           option the kernel will use a smaller kernel stack size. The reduced
 370           size is 8kb instead of 16kb. This allows to run more threads on a
 371           system and reduces the pressure on the memory management for higher
 372           order page allocations.
 373
 374           Say N if you are unsure.
 375
 376 config CHECK_STACK
 377         def_bool y
 378         prompt "Detect kernel stack overflow"
 379         help
 380           This option enables the compiler option -mstack-guard and
 381           -mstack-size if they are available. If the compiler supports them
 382           it will emit additional code to each function prolog to trigger
 383           an illegal operation if the kernel stack is about to overflow.
 384
 385           Say N if you are unsure.
 386
 387 config STACK_GUARD
 388         int "Size of the guard area (128-1024)"
 389         range 128 1024
 390         depends on CHECK_STACK
 391         default "256"
 392         help
 393           This allows you to specify the size of the guard area at the lower
 394           end of the kernel stack. If the kernel stack points into the guard
 395           area on function entry an illegal operation is triggered. The size
 396           needs to be a power of 2. Please keep in mind that the size of an
 397           interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
 398           The minimum size for the stack guard should be 256 for 31 bit and
 399           512 for 64 bit.
 400
 401 config WARN_DYNAMIC_STACK
 402         def_bool n
 403         prompt "Emit compiler warnings for function with dynamic stack usage"
 404         help
 405           This option enables the compiler option -mwarn-dynamicstack. If the
 406           compiler supports this options generates warnings for functions
 407           that dynamically allocate stack space using alloca.
 408
 409           Say N if you are unsure.
 410
 411 endmenu
 412
 413 menu "I/O subsystem"
 414
 415 config QDIO
 416         def_tristate y
 417         prompt "QDIO support"
 418         ---help---
 419           This driver provides the Queued Direct I/O base support for
 420           IBM System z.
 421
 422           To compile this driver as a module, choose M here: the
 423           module will be called qdio.
 424
 425           If unsure, say Y.
 426
 427 config CHSC_SCH
 428         def_tristate m
 429         prompt "Support for CHSC subchannels"
 430         help
 431           This driver allows usage of CHSC subchannels. A CHSC subchannel
 432           is usually present on LPAR only.
 433           The driver creates a device /dev/chsc, which may be used to
 434           obtain I/O configuration information about the machine and
 435           to issue asynchronous chsc commands (DANGEROUS).
 436           You will usually only want to use this interface on a special
 437           LPAR designated for system management.
 438
 439           To compile this driver as a module, choose M here: the
 440           module will be called chsc_sch.
 441
 442           If unsure, say N.
 443
 444 config SCM_BUS
 445         def_bool y
 446         depends on 64BIT
 447         prompt "SCM bus driver"
 448         help
 449           Bus driver for Storage Class Memory.
 450
 451 config EADM_SCH
 452         def_tristate m
 453         prompt "Support for EADM subchannels"
 454         depends on SCM_BUS
 455         help
 456           This driver allows usage of EADM subchannels. EADM subchannels act
 457           as a communication vehicle for SCM increments.
 458
 459           To compile this driver as a module, choose M here: the
 460           module will be called eadm_sch.
 461
 462 endmenu
 463
 464 menu "Dump support"
 465
 466 config CRASH_DUMP
 467         bool "kernel crash dumps"
 468         depends on 64BIT && SMP
 469         select KEXEC
 470         help
 471           Generate crash dump after being started by kexec.
 472           Crash dump kernels are loaded in the main kernel with kexec-tools
 473           into a specially reserved region and then later executed after
 474           a crash by kdump/kexec.
 475           For more details see Documentation/kdump/kdump.txt
 476
 477 config ZFCPDUMP
 478         def_bool n
 479         prompt "zfcpdump support"
 480         select SMP
 481         help
 482           Select this option if you want to build an zfcpdump enabled kernel.
 483           Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
 484
 485 endmenu
 486
 487 menu "Executable file formats / Emulations"
 488
 489 source "fs/Kconfig.binfmt"
 490
 491 config SECCOMP
 492         def_bool y
 493         prompt "Enable seccomp to safely compute untrusted bytecode"
 494         depends on PROC_FS
 495         help
 496           This kernel feature is useful for number crunching applications
 497           that may need to compute untrusted bytecode during their
 498           execution. By using pipes or other transports made available to
 499           the process as file descriptors supporting the read/write
 500           syscalls, it's possible to isolate those applications in
 501           their own address space using seccomp. Once seccomp is
 502           enabled via /proc/<pid>/seccomp, it cannot be disabled
 503           and the task is only allowed to execute a few safe syscalls
 504           defined by each seccomp mode.
 505
 506           If unsure, say Y.
 507
 508 endmenu
 509
 510 menu "Power Management"
 511
 512 config ARCH_HIBERNATION_POSSIBLE
 513         def_bool y if 64BIT
 514
 515 source "kernel/power/Kconfig"
 516
 517 endmenu
 518
 519 source "net/Kconfig"
 520
 521 config PCMCIA
 522         def_bool n
 523
 524 config CCW
 525         def_bool y
 526
 527 source "drivers/Kconfig"
 528
 529 source "fs/Kconfig"
 530
 531 source "arch/s390/Kconfig.debug"
 532
 533 source "security/Kconfig"
 534
 535 source "crypto/Kconfig"
 536
 537 source "lib/Kconfig"
 538
 539 menu "Virtualization"
 540
 541 config PFAULT
 542         def_bool y
 543         prompt "Pseudo page fault support"
 544         help
 545           Select this option, if you want to use PFAULT pseudo page fault
 546           handling under VM. If running native or in LPAR, this option
 547           has no effect. If your VM does not support PFAULT, PAGEEX
 548           pseudo page fault handling will be used.
 549           Note that VM 4.2 supports PFAULT but has a bug in its
 550           implementation that causes some problems.
 551           Everybody who wants to run Linux under VM != VM4.2 should select
 552           this option.
 553
 554 config SHARED_KERNEL
 555         bool "VM shared kernel support"
 556         depends on !JUMP_LABEL
 557         help
 558           Select this option, if you want to share the text segment of the
 559           Linux kernel between different VM guests. This reduces memory
 560           usage with lots of guests but greatly increases kernel size.
 561           Also if a kernel was IPL'ed from a shared segment the kexec system
 562           call will not work.
 563           You should only select this option if you know what you are
 564           doing and want to exploit this feature.
 565
 566 config CMM
 567         def_tristate n
 568         prompt "Cooperative memory management"
 569         help
 570           Select this option, if you want to enable the kernel interface
 571           to reduce the memory size of the system. This is accomplished
 572           by allocating pages of memory and put them "on hold". This only
 573           makes sense for a system running under VM where the unused pages
 574           will be reused by VM for other guest systems. The interface
 575           allows an external monitor to balance memory of many systems.
 576           Everybody who wants to run Linux under VM should select this
 577           option.
 578
 579 config CMM_IUCV
 580         def_bool y
 581         prompt "IUCV special message interface to cooperative memory management"
 582         depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
 583         help
 584           Select this option to enable the special message interface to
 585           the cooperative memory management.
 586
 587 config APPLDATA_BASE
 588         def_bool n
 589         prompt "Linux - VM Monitor Stream, base infrastructure"
 590         depends on PROC_FS
 591         help
 592           This provides a kernel interface for creating and updating z/VM APPLDATA
 593           monitor records. The monitor records are updated at certain time
 594           intervals, once the timer is started.
 595           Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
 596           i.e. enables or disables monitoring on the Linux side.
 597           A custom interval value (in seconds) can be written to
 598           /proc/appldata/interval.
 599
 600           Defaults are 60 seconds interval and timer off.
 601           The /proc entries can also be read from, showing the current settings.
 602
 603 config APPLDATA_MEM
 604         def_tristate m
 605         prompt "Monitor memory management statistics"
 606         depends on APPLDATA_BASE && VM_EVENT_COUNTERS
 607         help
 608           This provides memory management related data to the Linux - VM Monitor
 609           Stream, like paging/swapping rate, memory utilisation, etc.
 610           Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
 611           APPLDATA monitor record, i.e. enables or disables monitoring this record
 612           on the z/VM side.
 613
 614           Default is disabled.
 615           The /proc entry can also be read from, showing the current settings.
 616
 617           This can also be compiled as a module, which will be called
 618           appldata_mem.o.
 619
 620 config APPLDATA_OS
 621         def_tristate m
 622         prompt "Monitor OS statistics"
 623         depends on APPLDATA_BASE
 624         help
 625           This provides OS related data to the Linux - VM Monitor Stream, like
 626           CPU utilisation, etc.
 627           Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
 628           APPLDATA monitor record, i.e. enables or disables monitoring this record
 629           on the z/VM side.
 630
 631           Default is disabled.
 632           This can also be compiled as a module, which will be called
 633           appldata_os.o.
 634
 635 config APPLDATA_NET_SUM
 636         def_tristate m
 637         prompt "Monitor overall network statistics"
 638         depends on APPLDATA_BASE && NET
 639         help
 640           This provides network related data to the Linux - VM Monitor Stream,
 641           currently there is only a total sum of network I/O statistics, no
 642           per-interface data.
 643           Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
 644           APPLDATA monitor record, i.e. enables or disables monitoring this record
 645           on the z/VM side.
 646
 647           Default is disabled.
 648           This can also be compiled as a module, which will be called
 649           appldata_net_sum.o.
 650
 651 config S390_HYPFS_FS
 652         def_bool y
 653         prompt "s390 hypervisor file system support"
 654         select SYS_HYPERVISOR
 655         help
 656           This is a virtual file system intended to provide accounting
 657           information in an s390 hypervisor environment.
 658
 659 source "arch/s390/kvm/Kconfig"
 660
 661 config S390_GUEST
 662         def_bool y
 663         prompt "s390 support for virtio devices (EXPERIMENTAL)"
 664         depends on 64BIT && EXPERIMENTAL
 665         select VIRTUALIZATION
 666         select VIRTIO
 667         select VIRTIO_CONSOLE
 668         help
 669           Enabling this option adds support for virtio based paravirtual device
 670           drivers on s390.
 671
 672           Select this option if you want to run the kernel as a guest under
 673           the KVM hypervisor.
 674
 675 endmenu