Select this to enable optimizations for model z800/z900 (2064 and 2066 series). This will enable some optimizations that are not available on older ESA/390 (31 Bit) only CPUs.
Select this to enable optimizations for model z890/z990 (2084 and 2086 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM System z9 (2094 and 2096 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM System z10 (2097 and 2098 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM zEnterprise 114 and 196 (2818 and 2817 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM zBC12 and zEC12 (2828 and 2827 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM z13s and z13 (2965 and 2964 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM z14 ZR1 and z14 (3907 and 3906 series). The kernel will be slightly faster but will not work on older machines.
Select this to enable optimizations for IBM z15 (8562 and 8561 series). The kernel will be slightly faster but will not work on older machines.
Cause the compiler to tune (-mtune) the generated code for a machine. This will make the code run faster on the selected machine but somewhat slower on other machines. This option only changes how the compiler emits instructions, not the selection of instructions itself, so the resulting kernel will run on all other machines.
Tune the generated code for the target processor for which the kernel will be compiled.
Select this option if you want to enable your system kernel to handle system-calls from ELF binaries for 31 bit ESA. This option (and some other stuff like libraries and such) is needed for executing 31 bit applications. It is safe to say "Y".
This allows you to specify the maximum number of CPUs which this kernel will support. The maximum supported value is 512 and the minimum value which makes sense is 2. This is purely to save memory - each supported CPU adds approximately sixteen kilobytes to the kernel image.
Enable NUMA support This option adds NUMA support to the kernel.
Topology scheduler support improves the CPU scheduler's decision making when dealing with machines that have multi-threading, multiple cores or multiple books.
Enable the kexec file based system call. In contrast to the normal kexec system call this system call takes file descriptors for the kernel and initramfs as arguments.
This option makes kernel signature verification mandatory for the kexec_file_load() syscall. In addition to that option, you need to enable signature verification for the corresponding kernel image type being loaded in order for this to work.
Enable the s390 architectural random number generation API to provide random data for all consumers within the Linux kernel. When enabled the arch_random_* functions declared in linux/random.h are implemented. The implementation is based on the s390 CPACF instruction subfunction TRNG which provides a real true random number generator. If unsure, say Y.
If this option is selected the kernel will switch to a modified branch prediction mode if the firmware interface is available. The modified branch prediction mode improves the behaviour in regard to speculative execution. With the option enabled the kernel parameter "nobp=0" or "nospec" can be used to run the kernel in the normal branch prediction mode. With the option disabled the modified branch prediction mode is enabled with the "nobp=1" kernel parameter. If unsure, say N.
Compile the kernel with the expoline compiler options to guard against kernel-to-user data leaks by avoiding speculative indirect branches. Requires a compiler with -mindirect-branch=thunk support for full protection. The kernel may run slower. If unsure, say N.
This builds a kernel image that retains relocation information so it can be loaded at an arbitrary address. The kernel is linked as a position-independent executable (PIE) and contains dynamic relocations which are processed early in the bootup process. The relocations make the kernel image about 15% larger (compressed 10%), but are discarded at runtime.
In support of Kernel Address Space Layout Randomization (KASLR), this randomizes the address at which the kernel image is loaded, as a security feature that deters exploit attempts relying on knowledge of the location of kernel internals.
This option specifies the maximum supported size of physical memory in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB). Increasing the number of bits also increases the kernel image size. By default 46 bits (64TB) are supported.
This option enables the compiler option -mkernel-backchain if it is available. If the option is available the compiler supports the new stack layout which dramatically reduces the minimum stack frame size. With an old compiler a non-leaf function needs a minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With -mkernel-backchain the minimum size drops to 16 byte on 31 bit and 24 byte on 64 bit. Say Y if you are unsure.
This option enables the compiler option -mstack-guard and -mstack-size if they are available. If the compiler supports them it will emit additional code to each function prolog to trigger an illegal operation if the kernel stack is about to overflow. Say N if you are unsure.
This allows you to specify the size of the guard area at the lower end of the kernel stack. If the kernel stack points into the guard area on function entry an illegal operation is triggered. The size needs to be a power of 2. Please keep in mind that the size of an interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit. The minimum size for the stack guard should be 256 for 31 bit and 512 for 64 bit.
This option enables the compiler option -mwarn-dynamicstack. If the compiler supports this options generates warnings for functions that dynamically allocate stack space using alloca. Say N if you are unsure.
This driver provides the Queued Direct I/O base support for IBM System z. To compile this driver as a module, choose M here: the module will be called qdio. If unsure, say Y.
This allows you to specify the maximum number of PCI functions which this kernel will support.
This driver allows usage of CHSC subchannels. A CHSC subchannel is usually present on LPAR only. The driver creates a device /dev/chsc, which may be used to obtain I/O configuration information about the machine and to issue asynchronous chsc commands (DANGEROUS). You will usually only want to use this interface on a special LPAR designated for system management. To compile this driver as a module, choose M here: the module will be called chsc_sch. If unsure, say N.
Bus driver for Storage Class Memory.
This driver allows usage of EADM subchannels. EADM subchannels act as a communication vehicle for SCM increments. To compile this driver as a module, choose M here: the module will be called eadm_sch.
This driver allows usage of I/O subchannels via VFIO-CCW. To compile this driver as a module, choose M here: the module will be called vfio_ccw.
This driver grants access to Adjunct Processor (AP) devices via the VFIO mediated device interface. To compile this driver as a module, choose M here: the module will be called vfio_ap.
Generate crash dump after being started by kexec. Crash dump kernels are loaded in the main kernel with kexec-tools into a specially reserved region and then later executed after a crash by kdump/kexec. Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this. This option also enables s390 zfcpdump. See also <file:Documentation/s390/zfcpdump.rst>
Select this option, if you want to be able to run this kernel as a protected virtualization KVM guest. Protected virtualization capable machines have a mini hypervisor located at machine level (an ultravisor). With help of the Ultravisor, KVM will be able to run "protected" VMs, special VMs whose memory and management data are unavailable to KVM.
Select this option, if you want to use PFAULT pseudo page fault handling under VM. If running native or in LPAR, this option has no effect. If your VM does not support PFAULT, PAGEEX pseudo page fault handling will be used. Note that VM 4.2 supports PFAULT but has a bug in its implementation that causes some problems. Everybody who wants to run Linux under VM != VM4.2 should select this option.
Select this option, if you want to enable the kernel interface to reduce the memory size of the system. This is accomplished by allocating pages of memory and put them "on hold". This only makes sense for a system running under VM where the unused pages will be reused by VM for other guest systems. The interface allows an external monitor to balance memory of many systems. Everybody who wants to run Linux under VM should select this option.
Select this option to enable the special message interface to the cooperative memory management.
This provides a kernel interface for creating and updating z/VM APPLDATA monitor records. The monitor records are updated at certain time intervals, once the timer is started. Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer, i.e. enables or disables monitoring on the Linux side. A custom interval value (in seconds) can be written to /proc/appldata/interval. Defaults are 60 seconds interval and timer off. The /proc entries can also be read from, showing the current settings.
This provides memory management related data to the Linux - VM Monitor Stream, like paging/swapping rate, memory utilisation, etc. Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side. Default is disabled. The /proc entry can also be read from, showing the current settings. This can also be compiled as a module, which will be called appldata_mem.o.
This provides OS related data to the Linux - VM Monitor Stream, like CPU utilisation, etc. Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side. Default is disabled. This can also be compiled as a module, which will be called appldata_os.o.
This provides network related data to the Linux - VM Monitor Stream, currently there is only a total sum of network I/O statistics, no per-interface data. Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side. Default is disabled. This can also be compiled as a module, which will be called appldata_net_sum.o.
This is a virtual file system intended to provide accounting information in an s390 hypervisor environment.
Enabling this option adds support for virtio based paravirtual device drivers on s390. Select this option if you want to run the kernel as a guest under the KVM hypervisor.
This option enables s390 specific stack unwinder testing kernel module. This option is not useful for distributions or general kernels, but only for kernel developers working on architecture code. Say N if you are unsure.