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_STRICT_KERNEL_RWX
  77         select ARCH_HAS_STRICT_MODULE_RWX
  78         select ARCH_HAS_SYSCALL_WRAPPER
  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 HAVE_DYNAMIC_FTRACE
 144         select HAVE_DYNAMIC_FTRACE_WITH_REGS
 145         select HAVE_EFFICIENT_UNALIGNED_ACCESS
 146         select HAVE_FENTRY
 147         select HAVE_FTRACE_MCOUNT_RECORD
 148         select HAVE_FUNCTION_GRAPH_TRACER
 149         select HAVE_FUNCTION_TRACER
 150         select HAVE_FUTEX_CMPXCHG if FUTEX
 151         select HAVE_GCC_PLUGINS
 152         select HAVE_KERNEL_BZIP2
 153         select HAVE_KERNEL_GZIP
 154         select HAVE_KERNEL_LZ4
 155         select HAVE_KERNEL_LZMA
 156         select HAVE_KERNEL_LZO
 157         select HAVE_KERNEL_UNCOMPRESSED
 158         select HAVE_KERNEL_XZ
 159         select HAVE_KPROBES
 160         select HAVE_KRETPROBES
 161         select HAVE_KVM
 162         select HAVE_LIVEPATCH
 163         select HAVE_PERF_REGS
 164         select HAVE_PERF_USER_STACK_DUMP
 165         select HAVE_MEMBLOCK_NODE_MAP
 166         select HAVE_MEMBLOCK_PHYS_MAP
 167         select HAVE_MOD_ARCH_SPECIFIC
 168         select HAVE_NOP_MCOUNT
 169         select HAVE_OPROFILE
 170         select HAVE_PCI
 171         select HAVE_PERF_EVENTS
 172         select HAVE_REGS_AND_STACK_ACCESS_API
 173         select HAVE_RSEQ
 174         select HAVE_SYSCALL_TRACEPOINTS
 175         select HAVE_VIRT_CPU_ACCOUNTING
 176         select IOMMU_HELPER             if PCI
 177         select IOMMU_SUPPORT            if PCI
 178         select MODULES_USE_ELF_RELA
 179         select NEED_DMA_MAP_STATE       if PCI
 180         select NEED_SG_DMA_LENGTH       if PCI
 181         select OLD_SIGACTION
 182         select OLD_SIGSUSPEND3
 183         select PCI_DOMAINS              if PCI
 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         select HAVE_UID16
 384         depends on MULTIUSER
 385         help
 386           Select this option if you want to enable your system kernel to
 387           handle system-calls from ELF binaries for 31 bit ESA.  This option
 388           (and some other stuff like libraries and such) is needed for
 389           executing 31 bit applications.  It is safe to say "Y".
 390
 391 config SYSVIPC_COMPAT
 392         def_bool y if COMPAT && SYSVIPC
 393
 394 config SMP
 395         def_bool y
 396         prompt "Symmetric multi-processing support"
 397         ---help---
 398           This enables support for systems with more than one CPU. If you have
 399           a system with only one CPU, like most personal computers, say N. If
 400           you have a system with more than one CPU, say Y.
 401
 402           If you say N here, the kernel will run on uni- and multiprocessor
 403           machines, but will use only one CPU of a multiprocessor machine. If
 404           you say Y here, the kernel will run on many, but not all,
 405           uniprocessor machines. On a uniprocessor machine, the kernel
 406           will run faster if you say N here.
 407
 408           See also the SMP-HOWTO available at
 409           <http://www.tldp.org/docs.html#howto>.
 410
 411           Even if you don't know what to do here, say Y.
 412
 413 config NR_CPUS
 414         int "Maximum number of CPUs (2-512)"
 415         range 2 512
 416         depends on SMP
 417         default "64"
 418         help
 419           This allows you to specify the maximum number of CPUs which this
 420           kernel will support. The maximum supported value is 512 and the
 421           minimum value which makes sense is 2.
 422
 423           This is purely to save memory - each supported CPU adds
 424           approximately sixteen kilobytes to the kernel image.
 425
 426 config HOTPLUG_CPU
 427         def_bool y
 428         prompt "Support for hot-pluggable CPUs"
 429         depends on SMP
 430         help
 431           Say Y here to be able to turn CPUs off and on. CPUs
 432           can be controlled through /sys/devices/system/cpu/cpu#.
 433           Say N if you want to disable CPU hotplug.
 434
 435 # Some NUMA nodes have memory ranges that span
 436 # other nodes.  Even though a pfn is valid and
 437 # between a node's start and end pfns, it may not
 438 # reside on that node.  See memmap_init_zone()
 439 # for details. <- They meant memory holes!
 440 config NODES_SPAN_OTHER_NODES
 441         def_bool NUMA
 442
 443 config NUMA
 444         bool "NUMA support"
 445         depends on SMP && SCHED_TOPOLOGY
 446         default n
 447         help
 448           Enable NUMA support
 449
 450           This option adds NUMA support to the kernel.
 451
 452           An operation mode can be selected by appending
 453           numa=<method> to the kernel command line.
 454
 455           The default behaviour is identical to appending numa=plain to
 456           the command line. This will create just one node with all
 457           available memory and all CPUs in it.
 458
 459 config NODES_SHIFT
 460         int "Maximum NUMA nodes (as a power of 2)"
 461         range 1 10
 462         depends on NUMA
 463         default "4"
 464         help
 465           Specify the maximum number of NUMA nodes available on the target
 466           system. Increases memory reserved to accommodate various tables.
 467
 468 menu "Select NUMA modes"
 469         depends on NUMA
 470
 471 config NUMA_EMU
 472         bool "NUMA emulation"
 473         default y
 474         help
 475           Numa emulation mode will split the available system memory into
 476           equal chunks which then are distributed over the configured number
 477           of nodes in a round-robin manner.
 478
 479           The number of fake nodes is limited by the number of available memory
 480           chunks (i.e. memory size / fake size) and the number of supported
 481           nodes in the kernel.
 482
 483           The CPUs are assigned to the nodes in a way that partially respects
 484           the original machine topology (if supported by the machine).
 485           Fair distribution of the CPUs is not guaranteed.
 486
 487 config EMU_SIZE
 488         hex "NUMA emulation memory chunk size"
 489         default 0x10000000
 490         range 0x400000 0x100000000
 491         depends on NUMA_EMU
 492         help
 493           Select the default size by which the memory is chopped and then
 494           assigned to emulated NUMA nodes.
 495
 496           This can be overridden by specifying
 497
 498           emu_size=<n>
 499
 500           on the kernel command line where also suffixes K, M, G, and T are
 501           supported.
 502
 503 endmenu
 504
 505 config SCHED_SMT
 506         def_bool n
 507
 508 config SCHED_MC
 509         def_bool n
 510
 511 config SCHED_BOOK
 512         def_bool n
 513
 514 config SCHED_DRAWER
 515         def_bool n
 516
 517 config SCHED_TOPOLOGY
 518         def_bool y
 519         prompt "Topology scheduler support"
 520         depends on SMP
 521         select SCHED_SMT
 522         select SCHED_MC
 523         select SCHED_BOOK
 524         select SCHED_DRAWER
 525         help
 526           Topology scheduler support improves the CPU scheduler's decision
 527           making when dealing with machines that have multi-threading,
 528           multiple cores or multiple books.
 529
 530 source "kernel/Kconfig.hz"
 531
 532 config KEXEC
 533         def_bool y
 534         select KEXEC_CORE
 535
 536 config KEXEC_FILE
 537         bool "kexec file based system call"
 538         select KEXEC_CORE
 539         select BUILD_BIN2C
 540         depends on CRYPTO
 541         depends on CRYPTO_SHA256
 542         depends on CRYPTO_SHA256_S390
 543         help
 544           Enable the kexec file based system call. In contrast to the normal
 545           kexec system call this system call takes file descriptors for the
 546           kernel and initramfs as arguments.
 547
 548 config ARCH_HAS_KEXEC_PURGATORY
 549         def_bool y
 550         depends on KEXEC_FILE
 551
 552 config ARCH_RANDOM
 553         def_bool y
 554         prompt "s390 architectural random number generation API"
 555         help
 556           Enable the s390 architectural random number generation API
 557           to provide random data for all consumers within the Linux
 558           kernel.
 559
 560           When enabled the arch_random_* functions declared in linux/random.h
 561           are implemented. The implementation is based on the s390 CPACF
 562           instruction subfunction TRNG which provides a real true random
 563           number generator.
 564
 565           If unsure, say Y.
 566
 567 config KERNEL_NOBP
 568         def_bool n
 569         prompt "Enable modified branch prediction for the kernel by default"
 570         help
 571           If this option is selected the kernel will switch to a modified
 572           branch prediction mode if the firmware interface is available.
 573           The modified branch prediction mode improves the behaviour in
 574           regard to speculative execution.
 575
 576           With the option enabled the kernel parameter "nobp=0" or "nospec"
 577           can be used to run the kernel in the normal branch prediction mode.
 578
 579           With the option disabled the modified branch prediction mode is
 580           enabled with the "nobp=1" kernel parameter.
 581
 582           If unsure, say N.
 583
 584 config EXPOLINE
 585         def_bool n
 586         prompt "Avoid speculative indirect branches in the kernel"
 587         help
 588           Compile the kernel with the expoline compiler options to guard
 589           against kernel-to-user data leaks by avoiding speculative indirect
 590           branches.
 591           Requires a compiler with -mindirect-branch=thunk support for full
 592           protection. The kernel may run slower.
 593
 594           If unsure, say N.
 595
 596 choice
 597         prompt "Expoline default"
 598         depends on EXPOLINE
 599         default EXPOLINE_FULL
 600
 601 config EXPOLINE_OFF
 602         bool "spectre_v2=off"
 603
 604 config EXPOLINE_AUTO
 605         bool "spectre_v2=auto"
 606
 607 config EXPOLINE_FULL
 608         bool "spectre_v2=on"
 609
 610 endchoice
 611
 612 endmenu
 613
 614 menu "Memory setup"
 615
 616 config ARCH_SPARSEMEM_ENABLE
 617         def_bool y
 618         select SPARSEMEM_VMEMMAP_ENABLE
 619         select SPARSEMEM_VMEMMAP
 620
 621 config ARCH_SPARSEMEM_DEFAULT
 622         def_bool y
 623
 624 config ARCH_SELECT_MEMORY_MODEL
 625         def_bool y
 626
 627 config ARCH_ENABLE_MEMORY_HOTPLUG
 628         def_bool y if SPARSEMEM
 629
 630 config ARCH_ENABLE_MEMORY_HOTREMOVE
 631         def_bool y
 632
 633 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 634         def_bool y
 635
 636 config FORCE_MAX_ZONEORDER
 637         int
 638         default "9"
 639
 640 config MAX_PHYSMEM_BITS
 641         int "Maximum size of supported physical memory in bits (42-53)"
 642         range 42 53
 643         default "46"
 644         help
 645           This option specifies the maximum supported size of physical memory
 646           in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB).
 647           Increasing the number of bits also increases the kernel image size.
 648           By default 46 bits (64TB) are supported.
 649
 650 config PACK_STACK
 651         def_bool y
 652         prompt "Pack kernel stack"
 653         help
 654           This option enables the compiler option -mkernel-backchain if it
 655           is available. If the option is available the compiler supports
 656           the new stack layout which dramatically reduces the minimum stack
 657           frame size. With an old compiler a non-leaf function needs a
 658           minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
 659           -mkernel-backchain the minimum size drops to 16 byte on 31 bit
 660           and 24 byte on 64 bit.
 661
 662           Say Y if you are unsure.
 663
 664 config CHECK_STACK
 665         def_bool y
 666         depends on !VMAP_STACK
 667         prompt "Detect kernel stack overflow"
 668         help
 669           This option enables the compiler option -mstack-guard and
 670           -mstack-size if they are available. If the compiler supports them
 671           it will emit additional code to each function prolog to trigger
 672           an illegal operation if the kernel stack is about to overflow.
 673
 674           Say N if you are unsure.
 675
 676 config STACK_GUARD
 677         int "Size of the guard area (128-1024)"
 678         range 128 1024
 679         depends on CHECK_STACK
 680         default "256"
 681         help
 682           This allows you to specify the size of the guard area at the lower
 683           end of the kernel stack. If the kernel stack points into the guard
 684           area on function entry an illegal operation is triggered. The size
 685           needs to be a power of 2. Please keep in mind that the size of an
 686           interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
 687           The minimum size for the stack guard should be 256 for 31 bit and
 688           512 for 64 bit.
 689
 690 config WARN_DYNAMIC_STACK
 691         def_bool n
 692         prompt "Emit compiler warnings for function with dynamic stack usage"
 693         help
 694           This option enables the compiler option -mwarn-dynamicstack. If the
 695           compiler supports this options generates warnings for functions
 696           that dynamically allocate stack space using alloca.
 697
 698           Say N if you are unsure.
 699
 700 endmenu
 701
 702 menu "I/O subsystem"
 703
 704 config QDIO
 705         def_tristate y
 706         prompt "QDIO support"
 707         ---help---
 708           This driver provides the Queued Direct I/O base support for
 709           IBM System z.
 710
 711           To compile this driver as a module, choose M here: the
 712           module will be called qdio.
 713
 714           If unsure, say Y.
 715
 716 if PCI
 717
 718 config PCI_NR_FUNCTIONS
 719         int "Maximum number of PCI functions (1-4096)"
 720         range 1 4096
 721         default "128"
 722         help
 723           This allows you to specify the maximum number of PCI functions which
 724           this kernel will support.
 725
 726 endif   # PCI
 727
 728 config HAS_IOMEM
 729         def_bool PCI
 730
 731 config CHSC_SCH
 732         def_tristate m
 733         prompt "Support for CHSC subchannels"
 734         help
 735           This driver allows usage of CHSC subchannels. A CHSC subchannel
 736           is usually present on LPAR only.
 737           The driver creates a device /dev/chsc, which may be used to
 738           obtain I/O configuration information about the machine and
 739           to issue asynchronous chsc commands (DANGEROUS).
 740           You will usually only want to use this interface on a special
 741           LPAR designated for system management.
 742
 743           To compile this driver as a module, choose M here: the
 744           module will be called chsc_sch.
 745
 746           If unsure, say N.
 747
 748 config SCM_BUS
 749         def_bool y
 750         prompt "SCM bus driver"
 751         help
 752           Bus driver for Storage Class Memory.
 753
 754 config EADM_SCH
 755         def_tristate m
 756         prompt "Support for EADM subchannels"
 757         depends on SCM_BUS
 758         help
 759           This driver allows usage of EADM subchannels. EADM subchannels act
 760           as a communication vehicle for SCM increments.
 761
 762           To compile this driver as a module, choose M here: the
 763           module will be called eadm_sch.
 764
 765 config VFIO_CCW
 766         def_tristate n
 767         prompt "Support for VFIO-CCW subchannels"
 768         depends on S390_CCW_IOMMU && VFIO_MDEV
 769         help
 770           This driver allows usage of I/O subchannels via VFIO-CCW.
 771
 772           To compile this driver as a module, choose M here: the
 773           module will be called vfio_ccw.
 774
 775 config VFIO_AP
 776         def_tristate n
 777         prompt "VFIO support for AP devices"
 778         depends on S390_AP_IOMMU && VFIO_MDEV_DEVICE && KVM
 779         help
 780                 This driver grants access to Adjunct Processor (AP) devices
 781                 via the VFIO mediated device interface.
 782
 783                 To compile this driver as a module, choose M here: the module
 784                 will be called vfio_ap.
 785
 786 endmenu
 787
 788 menu "Dump support"
 789
 790 config CRASH_DUMP
 791         bool "kernel crash dumps"
 792         depends on SMP
 793         select KEXEC
 794         help
 795           Generate crash dump after being started by kexec.
 796           Crash dump kernels are loaded in the main kernel with kexec-tools
 797           into a specially reserved region and then later executed after
 798           a crash by kdump/kexec.
 799           Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
 800           This option also enables s390 zfcpdump.
 801           See also <file:Documentation/s390/zfcpdump.txt>
 802
 803 endmenu
 804
 805 config SECCOMP
 806         def_bool y
 807         prompt "Enable seccomp to safely compute untrusted bytecode"
 808         depends on PROC_FS
 809         help
 810           This kernel feature is useful for number crunching applications
 811           that may need to compute untrusted bytecode during their
 812           execution. By using pipes or other transports made available to
 813           the process as file descriptors supporting the read/write
 814           syscalls, it's possible to isolate those applications in
 815           their own address space using seccomp. Once seccomp is
 816           enabled via /proc/<pid>/seccomp, it cannot be disabled
 817           and the task is only allowed to execute a few safe syscalls
 818           defined by each seccomp mode.
 819
 820           If unsure, say Y.
 821
 822 menu "Power Management"
 823
 824 config ARCH_HIBERNATION_POSSIBLE
 825         def_bool y
 826
 827 source "kernel/power/Kconfig"
 828
 829 endmenu
 830
 831 config CCW
 832         def_bool y
 833
 834 config HAVE_PNETID
 835         tristate
 836         default (SMC || CCWGROUP)
 837
 838 menu "Virtualization"
 839
 840 config PFAULT
 841         def_bool y
 842         prompt "Pseudo page fault support"
 843         help
 844           Select this option, if you want to use PFAULT pseudo page fault
 845           handling under VM. If running native or in LPAR, this option
 846           has no effect. If your VM does not support PFAULT, PAGEEX
 847           pseudo page fault handling will be used.
 848           Note that VM 4.2 supports PFAULT but has a bug in its
 849           implementation that causes some problems.
 850           Everybody who wants to run Linux under VM != VM4.2 should select
 851           this option.
 852
 853 config CMM
 854         def_tristate n
 855         prompt "Cooperative memory management"
 856         help
 857           Select this option, if you want to enable the kernel interface
 858           to reduce the memory size of the system. This is accomplished
 859           by allocating pages of memory and put them "on hold". This only
 860           makes sense for a system running under VM where the unused pages
 861           will be reused by VM for other guest systems. The interface
 862           allows an external monitor to balance memory of many systems.
 863           Everybody who wants to run Linux under VM should select this
 864           option.
 865
 866 config CMM_IUCV
 867         def_bool y
 868         prompt "IUCV special message interface to cooperative memory management"
 869         depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
 870         help
 871           Select this option to enable the special message interface to
 872           the cooperative memory management.
 873
 874 config APPLDATA_BASE
 875         def_bool n
 876         prompt "Linux - VM Monitor Stream, base infrastructure"
 877         depends on PROC_FS
 878         help
 879           This provides a kernel interface for creating and updating z/VM APPLDATA
 880           monitor records. The monitor records are updated at certain time
 881           intervals, once the timer is started.
 882           Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
 883           i.e. enables or disables monitoring on the Linux side.
 884           A custom interval value (in seconds) can be written to
 885           /proc/appldata/interval.
 886
 887           Defaults are 60 seconds interval and timer off.
 888           The /proc entries can also be read from, showing the current settings.
 889
 890 config APPLDATA_MEM
 891         def_tristate m
 892         prompt "Monitor memory management statistics"
 893         depends on APPLDATA_BASE && VM_EVENT_COUNTERS
 894         help
 895           This provides memory management related data to the Linux - VM Monitor
 896           Stream, like paging/swapping rate, memory utilisation, etc.
 897           Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
 898           APPLDATA monitor record, i.e. enables or disables monitoring this record
 899           on the z/VM side.
 900
 901           Default is disabled.
 902           The /proc entry can also be read from, showing the current settings.
 903
 904           This can also be compiled as a module, which will be called
 905           appldata_mem.o.
 906
 907 config APPLDATA_OS
 908         def_tristate m
 909         prompt "Monitor OS statistics"
 910         depends on APPLDATA_BASE
 911         help
 912           This provides OS related data to the Linux - VM Monitor Stream, like
 913           CPU utilisation, etc.
 914           Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
 915           APPLDATA monitor record, i.e. enables or disables monitoring this record
 916           on the z/VM side.
 917
 918           Default is disabled.
 919           This can also be compiled as a module, which will be called
 920           appldata_os.o.
 921
 922 config APPLDATA_NET_SUM
 923         def_tristate m
 924         prompt "Monitor overall network statistics"
 925         depends on APPLDATA_BASE && NET
 926         help
 927           This provides network related data to the Linux - VM Monitor Stream,
 928           currently there is only a total sum of network I/O statistics, no
 929           per-interface data.
 930           Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
 931           APPLDATA monitor record, i.e. enables or disables monitoring this record
 932           on the z/VM side.
 933
 934           Default is disabled.
 935           This can also be compiled as a module, which will be called
 936           appldata_net_sum.o.
 937
 938 config S390_HYPFS_FS
 939         def_bool y
 940         prompt "s390 hypervisor file system support"
 941         select SYS_HYPERVISOR
 942         help
 943           This is a virtual file system intended to provide accounting
 944           information in an s390 hypervisor environment.
 945
 946 source "arch/s390/kvm/Kconfig"
 947
 948 config S390_GUEST
 949         def_bool y
 950         prompt "s390 support for virtio devices"
 951         select TTY
 952         select VIRTUALIZATION
 953         select VIRTIO
 954         select VIRTIO_CONSOLE
 955         help
 956           Enabling this option adds support for virtio based paravirtual device
 957           drivers on s390.
 958
 959           Select this option if you want to run the kernel as a guest under
 960           the KVM hypervisor.
 961
 962 endmenu