arch/s390/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 config MMU
   3         def_bool y
   4
   5 config ZONE_DMA
   6         def_bool y
   7
   8 config CPU_BIG_ENDIAN
   9         def_bool y
  10
  11 config LOCKDEP_SUPPORT
  12         def_bool y
  13
  14 config STACKTRACE_SUPPORT
  15         def_bool y
  16
  17 config RWSEM_GENERIC_SPINLOCK
  18         bool
  19
  20 config RWSEM_XCHGADD_ALGORITHM
  21         def_bool y
  22
  23 config ARCH_HAS_ILOG2_U32
  24         def_bool n
  25
  26 config ARCH_HAS_ILOG2_U64
  27         def_bool n
  28
  29 config GENERIC_HWEIGHT
  30         def_bool y
  31
  32 config GENERIC_BUG
  33         def_bool y if BUG
  34
  35 config GENERIC_BUG_RELATIVE_POINTERS
  36         def_bool y
  37
  38 config GENERIC_LOCKBREAK
  39         def_bool y if SMP && PREEMPT
  40
  41 config PGSTE
  42         def_bool y if KVM
  43
  44 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
  45         def_bool y
  46
  47 config AUDIT_ARCH
  48         def_bool y
  49
  50 config NO_IOPORT_MAP
  51         def_bool y
  52
  53 config PCI_QUIRKS
  54         def_bool n
  55
  56 config ARCH_SUPPORTS_UPROBES
  57         def_bool y
  58
  59 config KASAN_SHADOW_OFFSET
  60         hex
  61         depends on KASAN
  62         default 0x18000000000000 if KASAN_S390_4_LEVEL_PAGING
  63         default 0x30000000000
  64
  65 config S390
  66         def_bool y
  67         select ARCH_BINFMT_ELF_STATE
  68         select ARCH_HAS_DEVMEM_IS_ALLOWED
  69         select ARCH_HAS_ELF_RANDOMIZE
  70         select ARCH_HAS_FORTIFY_SOURCE
  71         select ARCH_HAS_GCOV_PROFILE_ALL
  72         select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
  73         select ARCH_HAS_KCOV
  74         select ARCH_HAS_PTE_SPECIAL
  75         select ARCH_HAS_SET_MEMORY
  76         select ARCH_HAS_SG_CHAIN
  77         select ARCH_HAS_STRICT_KERNEL_RWX
  78         select ARCH_HAS_STRICT_MODULE_RWX
  79         select ARCH_HAS_UBSAN_SANITIZE_ALL
  80         select ARCH_HAVE_NMI_SAFE_CMPXCHG
  81         select ARCH_INLINE_READ_LOCK
  82         select ARCH_INLINE_READ_LOCK_BH
  83         select ARCH_INLINE_READ_LOCK_IRQ
  84         select ARCH_INLINE_READ_LOCK_IRQSAVE
  85         select ARCH_INLINE_READ_TRYLOCK
  86         select ARCH_INLINE_READ_UNLOCK
  87         select ARCH_INLINE_READ_UNLOCK_BH
  88         select ARCH_INLINE_READ_UNLOCK_IRQ
  89         select ARCH_INLINE_READ_UNLOCK_IRQRESTORE
  90         select ARCH_INLINE_SPIN_LOCK
  91         select ARCH_INLINE_SPIN_LOCK_BH
  92         select ARCH_INLINE_SPIN_LOCK_IRQ
  93         select ARCH_INLINE_SPIN_LOCK_IRQSAVE
  94         select ARCH_INLINE_SPIN_TRYLOCK
  95         select ARCH_INLINE_SPIN_TRYLOCK_BH
  96         select ARCH_INLINE_SPIN_UNLOCK
  97         select ARCH_INLINE_SPIN_UNLOCK_BH
  98         select ARCH_INLINE_SPIN_UNLOCK_IRQ
  99         select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE
 100         select ARCH_INLINE_WRITE_LOCK
 101         select ARCH_INLINE_WRITE_LOCK_BH
 102         select ARCH_INLINE_WRITE_LOCK_IRQ
 103         select ARCH_INLINE_WRITE_LOCK_IRQSAVE
 104         select ARCH_INLINE_WRITE_TRYLOCK
 105         select ARCH_INLINE_WRITE_UNLOCK
 106         select ARCH_INLINE_WRITE_UNLOCK_BH
 107         select ARCH_INLINE_WRITE_UNLOCK_IRQ
 108         select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 109         select ARCH_SAVE_PAGE_KEYS if HIBERNATION
 110         select ARCH_SUPPORTS_ATOMIC_RMW
 111         select ARCH_SUPPORTS_NUMA_BALANCING
 112         select ARCH_USE_BUILTIN_BSWAP
 113         select ARCH_USE_CMPXCHG_LOCKREF
 114         select ARCH_WANTS_DYNAMIC_TASK_STRUCT
 115         select ARCH_WANT_IPC_PARSE_VERSION
 116         select BUILDTIME_EXTABLE_SORT
 117         select CLONE_BACKWARDS2
 118         select DYNAMIC_FTRACE if FUNCTION_TRACER
 119         select GENERIC_CLOCKEVENTS
 120         select GENERIC_CPU_AUTOPROBE
 121         select GENERIC_CPU_DEVICES if !SMP
 122         select GENERIC_CPU_VULNERABILITIES
 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 HAVE_ARCH_JUMP_LABEL_RELATIVE
 130         select HAVE_ARCH_KASAN
 131         select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES
 132         select HAVE_ARCH_SECCOMP_FILTER
 133         select HAVE_ARCH_SOFT_DIRTY
 134         select HAVE_ARCH_TRACEHOOK
 135         select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 136         select HAVE_ARCH_VMAP_STACK
 137         select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
 138         select HAVE_CMPXCHG_DOUBLE
 139         select HAVE_CMPXCHG_LOCAL
 140         select HAVE_COPY_THREAD_TLS
 141         select HAVE_DEBUG_KMEMLEAK
 142         select HAVE_DMA_CONTIGUOUS
 143         select DMA_DIRECT_OPS
 144         select HAVE_DYNAMIC_FTRACE
 145         select HAVE_DYNAMIC_FTRACE_WITH_REGS
 146         select HAVE_EFFICIENT_UNALIGNED_ACCESS
 147         select HAVE_FENTRY
 148         select HAVE_FTRACE_MCOUNT_RECORD
 149         select HAVE_FUNCTION_GRAPH_TRACER
 150         select HAVE_FUNCTION_TRACER
 151         select HAVE_FUTEX_CMPXCHG if FUTEX
 152         select HAVE_GCC_PLUGINS
 153         select HAVE_KERNEL_BZIP2
 154         select HAVE_KERNEL_GZIP
 155         select HAVE_KERNEL_LZ4
 156         select HAVE_KERNEL_LZMA
 157         select HAVE_KERNEL_LZO
 158         select HAVE_KERNEL_UNCOMPRESSED
 159         select HAVE_KERNEL_XZ
 160         select HAVE_KPROBES
 161         select HAVE_KRETPROBES
 162         select HAVE_KVM
 163         select HAVE_LIVEPATCH
 164         select HAVE_PERF_REGS
 165         select HAVE_PERF_USER_STACK_DUMP
 166         select HAVE_MEMBLOCK_NODE_MAP
 167         select HAVE_MEMBLOCK_PHYS_MAP
 168         select HAVE_MOD_ARCH_SPECIFIC
 169         select HAVE_NOP_MCOUNT
 170         select HAVE_OPROFILE
 171         select HAVE_PCI
 172         select HAVE_PERF_EVENTS
 173         select HAVE_REGS_AND_STACK_ACCESS_API
 174         select HAVE_RSEQ
 175         select HAVE_SYSCALL_TRACEPOINTS
 176         select HAVE_VIRT_CPU_ACCOUNTING
 177         select IOMMU_HELPER             if PCI
 178         select IOMMU_SUPPORT            if PCI
 179         select MODULES_USE_ELF_RELA
 180         select NEED_DMA_MAP_STATE       if PCI
 181         select NEED_SG_DMA_LENGTH       if PCI
 182         select OLD_SIGACTION
 183         select OLD_SIGSUSPEND3
 184         select PCI_MSI                  if PCI
 185         select SPARSE_IRQ
 186         select SYSCTL_EXCEPTION_TRACE
 187         select THREAD_INFO_IN_TASK
 188         select TTY
 189         select VIRT_CPU_ACCOUNTING
 190         select ARCH_HAS_SCALED_CPUTIME
 191         select VIRT_TO_BUS
 192         select HAVE_NMI
 193
 194
 195 config SCHED_OMIT_FRAME_POINTER
 196         def_bool y
 197
 198 config PGTABLE_LEVELS
 199         int
 200         default 5
 201
 202 source "kernel/livepatch/Kconfig"
 203
 204 menu "Processor type and features"
 205
 206 config HAVE_MARCH_Z900_FEATURES
 207         def_bool n
 208
 209 config HAVE_MARCH_Z990_FEATURES
 210         def_bool n
 211         select HAVE_MARCH_Z900_FEATURES
 212
 213 config HAVE_MARCH_Z9_109_FEATURES
 214         def_bool n
 215         select HAVE_MARCH_Z990_FEATURES
 216
 217 config HAVE_MARCH_Z10_FEATURES
 218         def_bool n
 219         select HAVE_MARCH_Z9_109_FEATURES
 220
 221 config HAVE_MARCH_Z196_FEATURES
 222         def_bool n
 223         select HAVE_MARCH_Z10_FEATURES
 224
 225 config HAVE_MARCH_ZEC12_FEATURES
 226         def_bool n
 227         select HAVE_MARCH_Z196_FEATURES
 228
 229 config HAVE_MARCH_Z13_FEATURES
 230         def_bool n
 231         select HAVE_MARCH_ZEC12_FEATURES
 232
 233 config HAVE_MARCH_Z14_FEATURES
 234         def_bool n
 235         select HAVE_MARCH_Z13_FEATURES
 236
 237 choice
 238         prompt "Processor type"
 239         default MARCH_Z196
 240
 241 config MARCH_Z900
 242         bool "IBM zSeries model z800 and z900"
 243         select HAVE_MARCH_Z900_FEATURES
 244         help
 245           Select this to enable optimizations for model z800/z900 (2064 and
 246           2066 series). This will enable some optimizations that are not
 247           available on older ESA/390 (31 Bit) only CPUs.
 248
 249 config MARCH_Z990
 250         bool "IBM zSeries model z890 and z990"
 251         select HAVE_MARCH_Z990_FEATURES
 252         help
 253           Select this to enable optimizations for model z890/z990 (2084 and
 254           2086 series). The kernel will be slightly faster but will not work
 255           on older machines.
 256
 257 config MARCH_Z9_109
 258         bool "IBM System z9"
 259         select HAVE_MARCH_Z9_109_FEATURES
 260         help
 261           Select this to enable optimizations for IBM System z9 (2094 and
 262           2096 series). The kernel will be slightly faster but will not work
 263           on older machines.
 264
 265 config MARCH_Z10
 266         bool "IBM System z10"
 267         select HAVE_MARCH_Z10_FEATURES
 268         help
 269           Select this to enable optimizations for IBM System z10 (2097 and
 270           2098 series). The kernel will be slightly faster but will not work
 271           on older machines.
 272
 273 config MARCH_Z196
 274         bool "IBM zEnterprise 114 and 196"
 275         select HAVE_MARCH_Z196_FEATURES
 276         help
 277           Select this to enable optimizations for IBM zEnterprise 114 and 196
 278           (2818 and 2817 series). The kernel will be slightly faster but will
 279           not work on older machines.
 280
 281 config MARCH_ZEC12
 282         bool "IBM zBC12 and zEC12"
 283         select HAVE_MARCH_ZEC12_FEATURES
 284         help
 285           Select this to enable optimizations for IBM zBC12 and zEC12 (2828 and
 286           2827 series). The kernel will be slightly faster but will not work on
 287           older machines.
 288
 289 config MARCH_Z13
 290         bool "IBM z13s and z13"
 291         select HAVE_MARCH_Z13_FEATURES
 292         help
 293           Select this to enable optimizations for IBM z13s and z13 (2965 and
 294           2964 series). The kernel will be slightly faster but will not work on
 295           older machines.
 296
 297 config MARCH_Z14
 298         bool "IBM z14 ZR1 and z14"
 299         select HAVE_MARCH_Z14_FEATURES
 300         help
 301           Select this to enable optimizations for IBM z14 ZR1 and z14 (3907
 302           and 3906 series). The kernel will be slightly faster but will not
 303           work on older machines.
 304
 305 endchoice
 306
 307 config MARCH_Z900_TUNE
 308         def_bool TUNE_Z900 || MARCH_Z900 && TUNE_DEFAULT
 309
 310 config MARCH_Z990_TUNE
 311         def_bool TUNE_Z990 || MARCH_Z990 && TUNE_DEFAULT
 312
 313 config MARCH_Z9_109_TUNE
 314         def_bool TUNE_Z9_109 || MARCH_Z9_109 && TUNE_DEFAULT
 315
 316 config MARCH_Z10_TUNE
 317         def_bool TUNE_Z10 || MARCH_Z10 && TUNE_DEFAULT
 318
 319 config MARCH_Z196_TUNE
 320         def_bool TUNE_Z196 || MARCH_Z196 && TUNE_DEFAULT
 321
 322 config MARCH_ZEC12_TUNE
 323         def_bool TUNE_ZEC12 || MARCH_ZEC12 && TUNE_DEFAULT
 324
 325 config MARCH_Z13_TUNE
 326         def_bool TUNE_Z13 || MARCH_Z13 && TUNE_DEFAULT
 327
 328 config MARCH_Z14_TUNE
 329         def_bool TUNE_Z14 || MARCH_Z14 && TUNE_DEFAULT
 330
 331 choice
 332         prompt "Tune code generation"
 333         default TUNE_DEFAULT
 334         help
 335           Cause the compiler to tune (-mtune) the generated code for a machine.
 336           This will make the code run faster on the selected machine but
 337           somewhat slower on other machines.
 338           This option only changes how the compiler emits instructions, not the
 339           selection of instructions itself, so the resulting kernel will run on
 340           all other machines.
 341
 342 config TUNE_DEFAULT
 343         bool "Default"
 344         help
 345           Tune the generated code for the target processor for which the kernel
 346           will be compiled.
 347
 348 config TUNE_Z900
 349         bool "IBM zSeries model z800 and z900"
 350
 351 config TUNE_Z990
 352         bool "IBM zSeries model z890 and z990"
 353
 354 config TUNE_Z9_109
 355         bool "IBM System z9"
 356
 357 config TUNE_Z10
 358         bool "IBM System z10"
 359
 360 config TUNE_Z196
 361         bool "IBM zEnterprise 114 and 196"
 362
 363 config TUNE_ZEC12
 364         bool "IBM zBC12 and zEC12"
 365
 366 config TUNE_Z13
 367         bool "IBM z13"
 368
 369 config TUNE_Z14
 370         bool "IBM z14"
 371
 372 endchoice
 373
 374 config 64BIT
 375         def_bool y
 376
 377 config COMPAT
 378         def_bool y
 379         prompt "Kernel support for 31 bit emulation"
 380         select COMPAT_BINFMT_ELF if BINFMT_ELF
 381         select ARCH_WANT_OLD_COMPAT_IPC
 382         select COMPAT_OLD_SIGACTION
 383         depends on MULTIUSER
 384         help
 385           Select this option if you want to enable your system kernel to
 386           handle system-calls from ELF binaries for 31 bit ESA.  This option
 387           (and some other stuff like libraries and such) is needed for
 388           executing 31 bit applications.  It is safe to say "Y".
 389
 390 config SYSVIPC_COMPAT
 391         def_bool y if COMPAT && SYSVIPC
 392
 393 config SMP
 394         def_bool y
 395         prompt "Symmetric multi-processing support"
 396         ---help---
 397           This enables support for systems with more than one CPU. If you have
 398           a system with only one CPU, like most personal computers, say N. If
 399           you have a system with more than one CPU, say Y.
 400
 401           If you say N here, the kernel will run on uni- and multiprocessor
 402           machines, but will use only one CPU of a multiprocessor machine. If
 403           you say Y here, the kernel will run on many, but not all,
 404           uniprocessor machines. On a uniprocessor machine, the kernel
 405           will run faster if you say N here.
 406
 407           See also the SMP-HOWTO available at
 408           <http://www.tldp.org/docs.html#howto>.
 409
 410           Even if you don't know what to do here, say Y.
 411
 412 config NR_CPUS
 413         int "Maximum number of CPUs (2-512)"
 414         range 2 512
 415         depends on SMP
 416         default "64"
 417         help
 418           This allows you to specify the maximum number of CPUs which this
 419           kernel will support. The maximum supported value is 512 and the
 420           minimum value which makes sense is 2.
 421
 422           This is purely to save memory - each supported CPU adds
 423           approximately sixteen kilobytes to the kernel image.
 424
 425 config HOTPLUG_CPU
 426         def_bool y
 427         prompt "Support for hot-pluggable CPUs"
 428         depends on SMP
 429         help
 430           Say Y here to be able to turn CPUs off and on. CPUs
 431           can be controlled through /sys/devices/system/cpu/cpu#.
 432           Say N if you want to disable CPU hotplug.
 433
 434 # Some NUMA nodes have memory ranges that span
 435 # other nodes.  Even though a pfn is valid and
 436 # between a node's start and end pfns, it may not
 437 # reside on that node.  See memmap_init_zone()
 438 # for details. <- They meant memory holes!
 439 config NODES_SPAN_OTHER_NODES
 440         def_bool NUMA
 441
 442 config NUMA
 443         bool "NUMA support"
 444         depends on SMP && SCHED_TOPOLOGY
 445         default n
 446         help
 447           Enable NUMA support
 448
 449           This option adds NUMA support to the kernel.
 450
 451           An operation mode can be selected by appending
 452           numa=<method> to the kernel command line.
 453
 454           The default behaviour is identical to appending numa=plain to
 455           the command line. This will create just one node with all
 456           available memory and all CPUs in it.
 457
 458 config NODES_SHIFT
 459         int "Maximum NUMA nodes (as a power of 2)"
 460         range 1 10
 461         depends on NUMA
 462         default "4"
 463         help
 464           Specify the maximum number of NUMA nodes available on the target
 465           system. Increases memory reserved to accommodate various tables.
 466
 467 menu "Select NUMA modes"
 468         depends on NUMA
 469
 470 config NUMA_EMU
 471         bool "NUMA emulation"
 472         default y
 473         help
 474           Numa emulation mode will split the available system memory into
 475           equal chunks which then are distributed over the configured number
 476           of nodes in a round-robin manner.
 477
 478           The number of fake nodes is limited by the number of available memory
 479           chunks (i.e. memory size / fake size) and the number of supported
 480           nodes in the kernel.
 481
 482           The CPUs are assigned to the nodes in a way that partially respects
 483           the original machine topology (if supported by the machine).
 484           Fair distribution of the CPUs is not guaranteed.
 485
 486 config EMU_SIZE
 487         hex "NUMA emulation memory chunk size"
 488         default 0x10000000
 489         range 0x400000 0x100000000
 490         depends on NUMA_EMU
 491         help
 492           Select the default size by which the memory is chopped and then
 493           assigned to emulated NUMA nodes.
 494
 495           This can be overridden by specifying
 496
 497           emu_size=<n>
 498
 499           on the kernel command line where also suffixes K, M, G, and T are
 500           supported.
 501
 502 endmenu
 503
 504 config SCHED_SMT
 505         def_bool n
 506
 507 config SCHED_MC
 508         def_bool n
 509
 510 config SCHED_BOOK
 511         def_bool n
 512
 513 config SCHED_DRAWER
 514         def_bool n
 515
 516 config SCHED_TOPOLOGY
 517         def_bool y
 518         prompt "Topology scheduler support"
 519         depends on SMP
 520         select SCHED_SMT
 521         select SCHED_MC
 522         select SCHED_BOOK
 523         select SCHED_DRAWER
 524         help
 525           Topology scheduler support improves the CPU scheduler's decision
 526           making when dealing with machines that have multi-threading,
 527           multiple cores or multiple books.
 528
 529 source kernel/Kconfig.hz
 530
 531 config KEXEC
 532         def_bool y
 533         select KEXEC_CORE
 534
 535 config KEXEC_FILE
 536         bool "kexec file based system call"
 537         select KEXEC_CORE
 538         select BUILD_BIN2C
 539         depends on CRYPTO
 540         depends on CRYPTO_SHA256
 541         depends on CRYPTO_SHA256_S390
 542         help
 543           Enable the kexec file based system call. In contrast to the normal
 544           kexec system call this system call takes file descriptors for the
 545           kernel and initramfs as arguments.
 546
 547 config ARCH_HAS_KEXEC_PURGATORY
 548         def_bool y
 549         depends on KEXEC_FILE
 550
 551 config ARCH_RANDOM
 552         def_bool y
 553         prompt "s390 architectural random number generation API"
 554         help
 555           Enable the s390 architectural random number generation API
 556           to provide random data for all consumers within the Linux
 557           kernel.
 558
 559           When enabled the arch_random_* functions declared in linux/random.h
 560           are implemented. The implementation is based on the s390 CPACF
 561           instruction subfunction TRNG which provides a real true random
 562           number generator.
 563
 564           If unsure, say Y.
 565
 566 config KERNEL_NOBP
 567         def_bool n
 568         prompt "Enable modified branch prediction for the kernel by default"
 569         help
 570           If this option is selected the kernel will switch to a modified
 571           branch prediction mode if the firmware interface is available.
 572           The modified branch prediction mode improves the behaviour in
 573           regard to speculative execution.
 574
 575           With the option enabled the kernel parameter "nobp=0" or "nospec"
 576           can be used to run the kernel in the normal branch prediction mode.
 577
 578           With the option disabled the modified branch prediction mode is
 579           enabled with the "nobp=1" kernel parameter.
 580
 581           If unsure, say N.
 582
 583 config EXPOLINE
 584         def_bool n
 585         prompt "Avoid speculative indirect branches in the kernel"
 586         help
 587           Compile the kernel with the expoline compiler options to guard
 588           against kernel-to-user data leaks by avoiding speculative indirect
 589           branches.
 590           Requires a compiler with -mindirect-branch=thunk support for full
 591           protection. The kernel may run slower.
 592
 593           If unsure, say N.
 594
 595 choice
 596         prompt "Expoline default"
 597         depends on EXPOLINE
 598         default EXPOLINE_FULL
 599
 600 config EXPOLINE_OFF
 601         bool "spectre_v2=off"
 602
 603 config EXPOLINE_AUTO
 604         bool "spectre_v2=auto"
 605
 606 config EXPOLINE_FULL
 607         bool "spectre_v2=on"
 608
 609 endchoice
 610
 611 endmenu
 612
 613 menu "Memory setup"
 614
 615 config ARCH_SPARSEMEM_ENABLE
 616         def_bool y
 617         select SPARSEMEM_VMEMMAP_ENABLE
 618         select SPARSEMEM_VMEMMAP
 619
 620 config ARCH_SPARSEMEM_DEFAULT
 621         def_bool y
 622
 623 config ARCH_SELECT_MEMORY_MODEL
 624         def_bool y
 625
 626 config ARCH_ENABLE_MEMORY_HOTPLUG
 627         def_bool y if SPARSEMEM
 628
 629 config ARCH_ENABLE_MEMORY_HOTREMOVE
 630         def_bool y
 631
 632 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 633         def_bool y
 634
 635 config FORCE_MAX_ZONEORDER
 636         int
 637         default "9"
 638
 639 config MAX_PHYSMEM_BITS
 640         int "Maximum size of supported physical memory in bits (42-53)"
 641         range 42 53
 642         default "46"
 643         help
 644           This option specifies the maximum supported size of physical memory
 645           in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB).
 646           Increasing the number of bits also increases the kernel image size.
 647           By default 46 bits (64TB) are supported.
 648
 649 config PACK_STACK
 650         def_bool y
 651         prompt "Pack kernel stack"
 652         help
 653           This option enables the compiler option -mkernel-backchain if it
 654           is available. If the option is available the compiler supports
 655           the new stack layout which dramatically reduces the minimum stack
 656           frame size. With an old compiler a non-leaf function needs a
 657           minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
 658           -mkernel-backchain the minimum size drops to 16 byte on 31 bit
 659           and 24 byte on 64 bit.
 660
 661           Say Y if you are unsure.
 662
 663 config CHECK_STACK
 664         def_bool y
 665         depends on !VMAP_STACK
 666         prompt "Detect kernel stack overflow"
 667         help
 668           This option enables the compiler option -mstack-guard and
 669           -mstack-size if they are available. If the compiler supports them
 670           it will emit additional code to each function prolog to trigger
 671           an illegal operation if the kernel stack is about to overflow.
 672
 673           Say N if you are unsure.
 674
 675 config STACK_GUARD
 676         int "Size of the guard area (128-1024)"
 677         range 128 1024
 678         depends on CHECK_STACK
 679         default "256"
 680         help
 681           This allows you to specify the size of the guard area at the lower
 682           end of the kernel stack. If the kernel stack points into the guard
 683           area on function entry an illegal operation is triggered. The size
 684           needs to be a power of 2. Please keep in mind that the size of an
 685           interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
 686           The minimum size for the stack guard should be 256 for 31 bit and
 687           512 for 64 bit.
 688
 689 config WARN_DYNAMIC_STACK
 690         def_bool n
 691         prompt "Emit compiler warnings for function with dynamic stack usage"
 692         help
 693           This option enables the compiler option -mwarn-dynamicstack. If the
 694           compiler supports this options generates warnings for functions
 695           that dynamically allocate stack space using alloca.
 696
 697           Say N if you are unsure.
 698
 699 endmenu
 700
 701 menu "I/O subsystem"
 702
 703 config QDIO
 704         def_tristate y
 705         prompt "QDIO support"
 706         ---help---
 707           This driver provides the Queued Direct I/O base support for
 708           IBM System z.
 709
 710           To compile this driver as a module, choose M here: the
 711           module will be called qdio.
 712
 713           If unsure, say Y.
 714
 715 if PCI
 716
 717 config PCI_NR_FUNCTIONS
 718         int "Maximum number of PCI functions (1-4096)"
 719         range 1 4096
 720         default "128"
 721         help
 722           This allows you to specify the maximum number of PCI functions which
 723           this kernel will support.
 724
 725 endif   # PCI
 726
 727 config PCI_DOMAINS
 728         def_bool PCI
 729
 730 config HAS_IOMEM
 731         def_bool PCI
 732
 733 config CHSC_SCH
 734         def_tristate m
 735         prompt "Support for CHSC subchannels"
 736         help
 737           This driver allows usage of CHSC subchannels. A CHSC subchannel
 738           is usually present on LPAR only.
 739           The driver creates a device /dev/chsc, which may be used to
 740           obtain I/O configuration information about the machine and
 741           to issue asynchronous chsc commands (DANGEROUS).
 742           You will usually only want to use this interface on a special
 743           LPAR designated for system management.
 744
 745           To compile this driver as a module, choose M here: the
 746           module will be called chsc_sch.
 747
 748           If unsure, say N.
 749
 750 config SCM_BUS
 751         def_bool y
 752         prompt "SCM bus driver"
 753         help
 754           Bus driver for Storage Class Memory.
 755
 756 config EADM_SCH
 757         def_tristate m
 758         prompt "Support for EADM subchannels"
 759         depends on SCM_BUS
 760         help
 761           This driver allows usage of EADM subchannels. EADM subchannels act
 762           as a communication vehicle for SCM increments.
 763
 764           To compile this driver as a module, choose M here: the
 765           module will be called eadm_sch.
 766
 767 config VFIO_CCW
 768         def_tristate n
 769         prompt "Support for VFIO-CCW subchannels"
 770         depends on S390_CCW_IOMMU && VFIO_MDEV
 771         help
 772           This driver allows usage of I/O subchannels via VFIO-CCW.
 773
 774           To compile this driver as a module, choose M here: the
 775           module will be called vfio_ccw.
 776
 777 config VFIO_AP
 778         def_tristate n
 779         prompt "VFIO support for AP devices"
 780         depends on S390_AP_IOMMU && VFIO_MDEV_DEVICE && KVM
 781         help
 782                 This driver grants access to Adjunct Processor (AP) devices
 783                 via the VFIO mediated device interface.
 784
 785                 To compile this driver as a module, choose M here: the module
 786                 will be called vfio_ap.
 787
 788 endmenu
 789
 790 menu "Dump support"
 791
 792 config CRASH_DUMP
 793         bool "kernel crash dumps"
 794         depends on SMP
 795         select KEXEC
 796         help
 797           Generate crash dump after being started by kexec.
 798           Crash dump kernels are loaded in the main kernel with kexec-tools
 799           into a specially reserved region and then later executed after
 800           a crash by kdump/kexec.
 801           Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
 802           This option also enables s390 zfcpdump.
 803           See also <file:Documentation/s390/zfcpdump.txt>
 804
 805 endmenu
 806
 807 config SECCOMP
 808         def_bool y
 809         prompt "Enable seccomp to safely compute untrusted bytecode"
 810         depends on PROC_FS
 811         help
 812           This kernel feature is useful for number crunching applications
 813           that may need to compute untrusted bytecode during their
 814           execution. By using pipes or other transports made available to
 815           the process as file descriptors supporting the read/write
 816           syscalls, it's possible to isolate those applications in
 817           their own address space using seccomp. Once seccomp is
 818           enabled via /proc/<pid>/seccomp, it cannot be disabled
 819           and the task is only allowed to execute a few safe syscalls
 820           defined by each seccomp mode.
 821
 822           If unsure, say Y.
 823
 824 menu "Power Management"
 825
 826 config ARCH_HIBERNATION_POSSIBLE
 827         def_bool y
 828
 829 source "kernel/power/Kconfig"
 830
 831 endmenu
 832
 833 config PCMCIA
 834         def_bool n
 835
 836 config CCW
 837         def_bool y
 838
 839 config HAVE_PNETID
 840         tristate
 841         default (SMC || CCWGROUP)
 842
 843 menu "Virtualization"
 844
 845 config PFAULT
 846         def_bool y
 847         prompt "Pseudo page fault support"
 848         help
 849           Select this option, if you want to use PFAULT pseudo page fault
 850           handling under VM. If running native or in LPAR, this option
 851           has no effect. If your VM does not support PFAULT, PAGEEX
 852           pseudo page fault handling will be used.
 853           Note that VM 4.2 supports PFAULT but has a bug in its
 854           implementation that causes some problems.
 855           Everybody who wants to run Linux under VM != VM4.2 should select
 856           this option.
 857
 858 config CMM
 859         def_tristate n
 860         prompt "Cooperative memory management"
 861         help
 862           Select this option, if you want to enable the kernel interface
 863           to reduce the memory size of the system. This is accomplished
 864           by allocating pages of memory and put them "on hold". This only
 865           makes sense for a system running under VM where the unused pages
 866           will be reused by VM for other guest systems. The interface
 867           allows an external monitor to balance memory of many systems.
 868           Everybody who wants to run Linux under VM should select this
 869           option.
 870
 871 config CMM_IUCV
 872         def_bool y
 873         prompt "IUCV special message interface to cooperative memory management"
 874         depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
 875         help
 876           Select this option to enable the special message interface to
 877           the cooperative memory management.
 878
 879 config APPLDATA_BASE
 880         def_bool n
 881         prompt "Linux - VM Monitor Stream, base infrastructure"
 882         depends on PROC_FS
 883         help
 884           This provides a kernel interface for creating and updating z/VM APPLDATA
 885           monitor records. The monitor records are updated at certain time
 886           intervals, once the timer is started.
 887           Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
 888           i.e. enables or disables monitoring on the Linux side.
 889           A custom interval value (in seconds) can be written to
 890           /proc/appldata/interval.
 891
 892           Defaults are 60 seconds interval and timer off.
 893           The /proc entries can also be read from, showing the current settings.
 894
 895 config APPLDATA_MEM
 896         def_tristate m
 897         prompt "Monitor memory management statistics"
 898         depends on APPLDATA_BASE && VM_EVENT_COUNTERS
 899         help
 900           This provides memory management related data to the Linux - VM Monitor
 901           Stream, like paging/swapping rate, memory utilisation, etc.
 902           Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
 903           APPLDATA monitor record, i.e. enables or disables monitoring this record
 904           on the z/VM side.
 905
 906           Default is disabled.
 907           The /proc entry can also be read from, showing the current settings.
 908
 909           This can also be compiled as a module, which will be called
 910           appldata_mem.o.
 911
 912 config APPLDATA_OS
 913         def_tristate m
 914         prompt "Monitor OS statistics"
 915         depends on APPLDATA_BASE
 916         help
 917           This provides OS related data to the Linux - VM Monitor Stream, like
 918           CPU utilisation, etc.
 919           Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
 920           APPLDATA monitor record, i.e. enables or disables monitoring this record
 921           on the z/VM side.
 922
 923           Default is disabled.
 924           This can also be compiled as a module, which will be called
 925           appldata_os.o.
 926
 927 config APPLDATA_NET_SUM
 928         def_tristate m
 929         prompt "Monitor overall network statistics"
 930         depends on APPLDATA_BASE && NET
 931         help
 932           This provides network related data to the Linux - VM Monitor Stream,
 933           currently there is only a total sum of network I/O statistics, no
 934           per-interface data.
 935           Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
 936           APPLDATA monitor record, i.e. enables or disables monitoring this record
 937           on the z/VM side.
 938
 939           Default is disabled.
 940           This can also be compiled as a module, which will be called
 941           appldata_net_sum.o.
 942
 943 config S390_HYPFS_FS
 944         def_bool y
 945         prompt "s390 hypervisor file system support"
 946         select SYS_HYPERVISOR
 947         help
 948           This is a virtual file system intended to provide accounting
 949           information in an s390 hypervisor environment.
 950
 951 source "arch/s390/kvm/Kconfig"
 952
 953 config S390_GUEST
 954         def_bool y
 955         prompt "s390 support for virtio devices"
 956         select TTY
 957         select VIRTUALIZATION
 958         select VIRTIO
 959         select VIRTIO_CONSOLE
 960         help
 961           Enabling this option adds support for virtio based paravirtual device
 962           drivers on s390.
 963
 964           Select this option if you want to run the kernel as a guest under
 965           the KVM hypervisor.
 966
 967 endmenu