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Diffstat (limited to 'kernel/Documentation/s390/kvm.txt')
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diff --git a/kernel/Documentation/s390/kvm.txt b/kernel/Documentation/s390/kvm.txt deleted file mode 100644 index 85f3280d7..000000000 --- a/kernel/Documentation/s390/kvm.txt +++ /dev/null @@ -1,125 +0,0 @@ -*** BIG FAT WARNING *** -The kvm module is currently in EXPERIMENTAL state for s390. This means that -the interface to the module is not yet considered to remain stable. Thus, be -prepared that we keep breaking your userspace application and guest -compatibility over and over again until we feel happy with the result. Make sure -your guest kernel, your host kernel, and your userspace launcher are in a -consistent state. - -This Documentation describes the unique ioctl calls to /dev/kvm, the resulting -kvm-vm file descriptors, and the kvm-vcpu file descriptors that differ from x86. - -1. ioctl calls to /dev/kvm -KVM does support the following ioctls on s390 that are common with other -architectures and do behave the same: -KVM_GET_API_VERSION -KVM_CREATE_VM (*) see note -KVM_CHECK_EXTENSION -KVM_GET_VCPU_MMAP_SIZE - -Notes: -* KVM_CREATE_VM may fail on s390, if the calling process has multiple -threads and has not called KVM_S390_ENABLE_SIE before. - -In addition, on s390 the following architecture specific ioctls are supported: -ioctl: KVM_S390_ENABLE_SIE -args: none -see also: include/linux/kvm.h -This call causes the kernel to switch on PGSTE in the user page table. This -operation is needed in order to run a virtual machine, and it requires the -calling process to be single-threaded. Note that the first call to KVM_CREATE_VM -will implicitly try to switch on PGSTE if the user process has not called -KVM_S390_ENABLE_SIE before. User processes that want to launch multiple threads -before creating a virtual machine have to call KVM_S390_ENABLE_SIE, or will -observe an error calling KVM_CREATE_VM. Switching on PGSTE is a one-time -operation, is not reversible, and will persist over the entire lifetime of -the calling process. It does not have any user-visible effect other than a small -performance penalty. - -2. ioctl calls to the kvm-vm file descriptor -KVM does support the following ioctls on s390 that are common with other -architectures and do behave the same: -KVM_CREATE_VCPU -KVM_SET_USER_MEMORY_REGION (*) see note -KVM_GET_DIRTY_LOG (**) see note - -Notes: -* kvm does only allow exactly one memory slot on s390, which has to start - at guest absolute address zero and at a user address that is aligned on any - page boundary. This hardware "limitation" allows us to have a few unique - optimizations. The memory slot doesn't have to be filled - with memory actually, it may contain sparse holes. That said, with different - user memory layout this does still allow a large flexibility when - doing the guest memory setup. -** KVM_GET_DIRTY_LOG doesn't work properly yet. The user will receive an empty -log. This ioctl call is only needed for guest migration, and we intend to -implement this one in the future. - -In addition, on s390 the following architecture specific ioctls for the kvm-vm -file descriptor are supported: -ioctl: KVM_S390_INTERRUPT -args: struct kvm_s390_interrupt * -see also: include/linux/kvm.h -This ioctl is used to submit a floating interrupt for a virtual machine. -Floating interrupts may be delivered to any virtual cpu in the configuration. -Only some interrupt types defined in include/linux/kvm.h make sense when -submitted as floating interrupts. The following interrupts are not considered -to be useful as floating interrupts, and a call to inject them will result in --EINVAL error code: program interrupts and interprocessor signals. Valid -floating interrupts are: -KVM_S390_INT_VIRTIO -KVM_S390_INT_SERVICE - -3. ioctl calls to the kvm-vcpu file descriptor -KVM does support the following ioctls on s390 that are common with other -architectures and do behave the same: -KVM_RUN -KVM_GET_REGS -KVM_SET_REGS -KVM_GET_SREGS -KVM_SET_SREGS -KVM_GET_FPU -KVM_SET_FPU - -In addition, on s390 the following architecture specific ioctls for the -kvm-vcpu file descriptor are supported: -ioctl: KVM_S390_INTERRUPT -args: struct kvm_s390_interrupt * -see also: include/linux/kvm.h -This ioctl is used to submit an interrupt for a specific virtual cpu. -Only some interrupt types defined in include/linux/kvm.h make sense when -submitted for a specific cpu. The following interrupts are not considered -to be useful, and a call to inject them will result in -EINVAL error code: -service processor calls and virtio interrupts. Valid interrupt types are: -KVM_S390_PROGRAM_INT -KVM_S390_SIGP_STOP -KVM_S390_RESTART -KVM_S390_SIGP_SET_PREFIX -KVM_S390_INT_EMERGENCY - -ioctl: KVM_S390_STORE_STATUS -args: unsigned long -see also: include/linux/kvm.h -This ioctl stores the state of the cpu at the guest real address given as -argument, unless one of the following values defined in include/linux/kvm.h -is given as argument: -KVM_S390_STORE_STATUS_NOADDR - the CPU stores its status to the save area in -absolute lowcore as defined by the principles of operation -KVM_S390_STORE_STATUS_PREFIXED - the CPU stores its status to the save area in -its prefix page just like the dump tool that comes with zipl. This is useful -to create a system dump for use with lkcdutils or crash. - -ioctl: KVM_S390_SET_INITIAL_PSW -args: struct kvm_s390_psw * -see also: include/linux/kvm.h -This ioctl can be used to set the processor status word (psw) of a stopped cpu -prior to running it with KVM_RUN. Note that this call is not required to modify -the psw during sie intercepts that fall back to userspace because struct kvm_run -does contain the psw, and this value is evaluated during reentry of KVM_RUN -after the intercept exit was recognized. - -ioctl: KVM_S390_INITIAL_RESET -args: none -see also: include/linux/kvm.h -This ioctl can be used to perform an initial cpu reset as defined by the -principles of operation. The target cpu has to be in stopped state. |