The Definitive KVM (Kernel-based Virtual Machine) API Documentation =================================================================== 1. General description The kvm API is a set of ioctls that are issued to control various aspects of a virtual machine. The ioctls belong to three classes - System ioctls: These query and set global attributes which affect the whole kvm subsystem. In addition a system ioctl is used to create virtual machines - VM ioctls: These query and set attributes that affect an entire virtual machine, for example memory layout. In addition a VM ioctl is used to create virtual cpus (vcpus). Only run VM ioctls from the same process (address space) that was used to create the VM. - vcpu ioctls: These query and set attributes that control the operation of a single virtual cpu. Only run vcpu ioctls from the same thread that was used to create the vcpu. 2. File descriptors The kvm API is centered around file descriptors. An initial open("/dev/kvm") obtains a handle to the kvm subsystem; this handle can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this handle will create a VM file descriptor which can be used to issue VM ioctls. A KVM_CREATE_VCPU ioctl on a VM fd will create a virtual cpu and return a file descriptor pointing to it. Finally, ioctls on a vcpu fd can be used to control the vcpu, including the important task of actually running guest code. In general file descriptors can be migrated among processes by means of fork() and the SCM_RIGHTS facility of unix domain socket. These kinds of tricks are explicitly not supported by kvm. While they will not cause harm to the host, their actual behavior is not guaranteed by the API. The only supported use is one virtual machine per process, and one vcpu per thread. 3. Extensions As of Linux 2.6.22, the KVM ABI has been stabilized: no backward incompatible change are allowed. However, there is an extension facility that allows backward-compatible extensions to the API to be queried and used. The extension mechanism is not based on on the Linux version number. Instead, kvm defines extension identifiers and a facility to query whether a particular extension identifier is available. If it is, a set of ioctls is available for application use. 4. API description This section describes ioctls that can be used to control kvm guests. For each ioctl, the following information is provided along with a description: Capability: which KVM extension provides this ioctl. Can be 'basic', which means that is will be provided by any kernel that supports API version 12 (see section 4.1), or a KVM_CAP_xyz constant, which means availability needs to be checked with KVM_CHECK_EXTENSION (see section 4.4). Architectures: which instruction set architectures provide this ioctl. x86 includes both i386 and x86_64. Type: system, vm, or vcpu. Parameters: what parameters are accepted by the ioctl. Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL) are not detailed, but errors with specific meanings are. 4.1 KVM_GET_API_VERSION Capability: basic Architectures: all Type: system ioctl Parameters: none Returns: the constant KVM_API_VERSION (=12) This identifies the API version as the stable kvm API. It is not expected that this number will change. However, Linux 2.6.20 and 2.6.21 report earlier versions; these are not documented and not supported. Applications should refuse to run if KVM_GET_API_VERSION returns a value other than 12. If this check passes, all ioctls described as 'basic' will be available. 4.2 KVM_CREATE_VM Capability: basic Architectures: all Type: system ioctl Parameters: none Returns: a VM fd that can be used to control the new virtual machine. The new VM has no virtual cpus and no memory. An mmap() of a VM fd will access the virtual machine's physical address space; offset zero corresponds to guest physical address zero. Use of mmap() on a VM fd is discouraged if userspace memory allocation (KVM_CAP_USER_MEMORY) is available. 4.3 KVM_GET_MSR_INDEX_LIST Capability: basic Architectures: x86 Type: system Parameters: struct kvm_msr_list (in/out) Returns: 0 on success; -1 on error Errors: E2BIG: the msr index list is to be to fit in the array specified by the user. struct kvm_msr_list { __u32 nmsrs; /* number of msrs in entries */ __u32 indices[0]; }; This ioctl returns the guest msrs that are supported. The list varies by kvm version and host processor, but does not change otherwise. The user fills in the size of the indices array in nmsrs, and in return kvm adjusts nmsrs to reflect the actual number of msrs and fills in the indices array with their numbers. Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are not returned in the MSR list, as different vcpus can have a different number of banks, as set via the KVM_X86_SETUP_MCE ioctl. 4.4 KVM_CHECK_EXTENSION Capability: basic Architectures: all Type: system ioctl Parameters: extension identifier (KVM_CAP_*) Returns: 0 if unsupported; 1 (or some other positive integer) if supported The API allows the application to query about extensions to the core kvm API. Userspace passes an extension identifier (an integer) and receives an integer that describes the extension availability. Generally 0 means no and 1 means yes, but some extensions may report additional information in the integer return value. 4.5 KVM_GET_VCPU_MMAP_SIZE Capability: basic Architectures: all Type: system ioctl Parameters: none Returns: size of vcpu mmap area, in bytes The KVM_RUN ioctl (cf.) communicates with userspace via a shared memory region. This ioctl returns the size of that region. See the KVM_RUN documentation for details. 4.6 KVM_SET_MEMORY_REGION Capability: basic Architectures: all Type: vm ioctl Parameters: struct kvm_memory_region (in) Returns: 0 on success, -1 on error This ioctl is obsolete and has been removed. 4.7 KVM_CREATE_VCPU Capability: basic Architectures: all Type: vm ioctl Parameters: vcpu id (apic id on x86) Returns: vcpu fd on success, -1 on error This API adds a vcpu to a virtual machine. The vcpu id is a small integer in the range [0, max_vcpus). The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time. The maximum possible value for max_vcpus can be retrieved using the KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time. If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4 cpus max. If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is same as the value returned from KVM_CAP_NR_VCPUS. On powerpc using book3s_hv mode, the vcpus are mapped onto virtual threads in one or more virtual CPU cores. (This is because the hardware requires all the hardware threads in a CPU core to be in the same partition.) The KVM_CAP_PPC_SMT capability indicates the number of vcpus per virtual core (vcore). The vcore id is obtained by dividing the vcpu id by the number of vcpus per vcore. The vcpus in a given vcore will always be in the same physical core as each other (though that might be a different physical core from time to time). Userspace can control the threading (SMT) mode of the guest by its allocation of vcpu ids. For example, if userspace wants single-threaded guest vcpus, it should make all vcpu ids be a multiple of the number of vcpus per vcore. On powerpc using book3s_hv mode, the vcpus are mapped onto virtual threads in one or more virtual CPU cores. (This is because the hardware requires all the hardware threads in a CPU core to be in the same partition.) The KVM_CAP_PPC_SMT capability indicates the number of vcpus per virtual core (vcore). The vcore id is obtained by dividing the vcpu id by the number of vcpus per vcore. The vcpus in a given vcore will always be in the same physical core as each other (though that might be a different physical core from time to time). Userspace can control the threading (SMT) mode of the guest by its allocation of vcpu ids. For example, if userspace wants single-threaded guest vcpus, it should make all vcpu ids be a multiple of the number of vcpus per vcore. 4.8 KVM_GET_DIRTY_LOG (vm ioctl) Capability: basic Architectures: x86 Type: vm ioctl Parameters: struct kvm_dirty_log (in/out) Returns: 0 on success, -1 on error /* for KVM_GET_DIRTY_LOG */ struct kvm_dirty_log { __u32 slot; __u32 padding; union { void __user *dirty_bitmap; /* one bit per page */ __u64 padding; }; }; Given a memory slot, return a bitmap containing any pages dirtied since the last call to this ioctl. Bit 0 is the first page in the memory slot. Ensure the entire structure is cleared to avoid padding issues. 4.9 KVM_SET_MEMORY_ALIAS Capability: basic Architectures: x86 Type: vm ioctl Parameters: struct kvm_memory_alias (in) Returns: 0 (success), -1 (error) This ioctl is obsolete and has been removed. 4.10 KVM_RUN Capability: basic Architectures: all Type: vcpu ioctl Parameters: none Returns: 0 on success, -1 on error Errors: EINTR: an unmasked signal is pending This ioctl is used to run a guest virtual cpu. While there are no explicit parameters, there is an implicit parameter block that can be obtained by mmap()ing the vcpu fd at offset 0, with the size given by KVM_GET_VCPU_MMAP_SIZE. The parameter block is formatted as a 'struct kvm_run' (see below). 4.11 KVM_GET_REGS Capability: basic Architectures: all Type: vcpu ioctl Parameters: struct kvm_regs (out) Returns: 0 on success, -1 on error Reads the general purpose registers from the vcpu. /* x86 */ struct kvm_regs { /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */ __u64 rax, rbx, rcx, rdx; __u64 rsi, rdi, rsp, rbp; __u64 r8, r9, r10, r11; __u64 r12, r13, r14, r15; __u64 rip, rflags; }; 4.12 KVM_SET_REGS Capability: basic Architectures: all Type: vcpu ioctl Parameters: struct kvm_regs (in) Returns: 0 on success, -1 on error Writes the general purpose registers into the vcpu. See KVM_GET_REGS for the data structure. 4.13 KVM_GET_SREGS Capability: basic Architectures: x86, ppc Type: vcpu ioctl Parameters: struct kvm_sregs (out) Returns: 0 on success, -1 on error Reads special registers from the vcpu. /* x86 */ struct kvm_sregs { struct kvm_segment cs, ds, es, fs, gs, ss; struct kvm_segment tr, ldt; struct kvm_dtable gdt, idt; __u64 cr0, cr2, cr3, cr4, cr8; __u64 efer; __u64 apic_base; __u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64]; }; /* ppc -- see arch/powerpc/include/asm/kvm.h */ interrupt_bitmap is a bitmap of pending external interrupts. At most one bit may be set. This interrupt has been acknowledged by the APIC but not yet injected into the cpu core. 4.14 KVM_SET_SREGS Capability: basic Architectures: x86, ppc Type: vcpu ioctl Parameters: struct kvm_sregs (in) Returns: 0 on success, -1 on error Writes special registers into the vcpu. See KVM_GET_SREGS for the data structures. 4.15 KVM_TRANSLATE Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_translation (in/out) Returns: 0 on success, -1 on error Translates a virtual address according to the vcpu's current address translation mode. struct kvm_translation { /* in */ __u64 linear_address; /* out */ __u64 physical_address; __u8 valid; __u8 writeable; __u8 usermode; __u8 pad[5]; }; 4.16 KVM_INTERRUPT Capability: basic Architectures: x86, ppc Type: vcpu ioctl Parameters: struct kvm_interrupt (in) Returns: 0 on success, -1 on error Queues a hardware interrupt vector to be injected. This is only useful if in-kernel local APIC or equivalent is not used. /* for KVM_INTERRUPT */ struct kvm_interrupt { /* in */ __u32 irq; }; X86: Note 'irq' is an interrupt vector, not an interrupt pin or line. PPC: Queues an external interrupt to be injected. This ioctl is overleaded with 3 different irq values: a) KVM_INTERRUPT_SET This injects an edge type external interrupt into the guest once it's ready to receive interrupts. When injected, the interrupt is done. b) KVM_INTERRUPT_UNSET This unsets any pending interrupt. Only available with KVM_CAP_PPC_UNSET_IRQ. c) KVM_INTERRUPT_SET_LEVEL This injects a level type external interrupt into the guest context. The interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET is triggered. Only available with KVM_CAP_PPC_IRQ_LEVEL. Note that any value for 'irq' other than the ones stated above is invalid and incurs unexpected behavior. 4.17 KVM_DEBUG_GUEST Capability: basic Architectures: none Type: vcpu ioctl Parameters: none) Returns: -1 on error Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead. 4.18 KVM_GET_MSRS Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_msrs (in/out) Returns: 0 on success, -1 on error Reads model-specific registers from the vcpu. Supported msr indices can be obtained using KVM_GET_MSR_INDEX_LIST. struct kvm_msrs { __u32 nmsrs; /* number of msrs in entries */ __u32 pad; struct kvm_msr_entry entries[0]; }; struct kvm_msr_entry { __u32 index; __u32 reserved; __u64 data; }; Application code should set the 'nmsrs' member (which indicates the size of the entries array) and the 'index' member of each array entry. kvm will fill in the 'data' member. 4.19 KVM_SET_MSRS Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_msrs (in) Returns: 0 on success, -1 on error Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the data structures. Application code should set the 'nmsrs' member (which indicates the size of the entries array), and the 'index' and 'data' members of each array entry. 4.20 KVM_SET_CPUID Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_cpuid (in) Returns: 0 on success, -1 on error Defines the vcpu responses to the cpuid instruction. Applications should use the KVM_SET_CPUID2 ioctl if available. struct kvm_cpuid_entry { __u32 function; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding; }; /* for KVM_SET_CPUID */ struct kvm_cpuid { __u32 nent; __u32 padding; struct kvm_cpuid_entry entries[0]; }; 4.21 KVM_SET_SIGNAL_MASK Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_signal_mask (in) Returns: 0 on success, -1 on error Defines which signals are blocked during execution of KVM_RUN. This signal mask temporarily overrides the threads signal mask. Any unblocked signal received (except SIGKILL and SIGSTOP, which retain their traditional behaviour) will cause KVM_RUN to return with -EINTR. Note the signal will only be delivered if not blocked by the original signal mask. /* for KVM_SET_SIGNAL_MASK */ struct kvm_signal_mask { __u32 len; __u8 sigset[0]; }; 4.22 KVM_GET_FPU Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_fpu (out) Returns: 0 on success, -1 on error Reads the floating point state from the vcpu. /* for KVM_GET_FPU and KVM_SET_FPU */ struct kvm_fpu { __u8 fpr[8][16]; __u16 fcw; __u16 fsw; __u8 ftwx; /* in fxsave format */ __u8 pad1; __u16 last_opcode; __u64 last_ip; __u64 last_dp; __u8 xmm[16][16]; __u32 mxcsr; __u32 pad2; }; 4.23 KVM_SET_FPU Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_fpu (in) Returns: 0 on success, -1 on error Writes the floating point state to the vcpu. /* for KVM_GET_FPU and KVM_SET_FPU */ struct kvm_fpu { __u8 fpr[8][16]; __u16 fcw; __u16 fsw; __u8 ftwx; /* in fxsave format */ __u8 pad1; __u16 last_opcode; __u64 last_ip; __u64 last_dp; __u8 xmm[16][16]; __u32 mxcsr; __u32 pad2; }; 4.24 KVM_CREATE_IRQCHIP Capability: KVM_CAP_IRQCHIP Architectures: x86, ia64 Type: vm ioctl Parameters: none Returns: 0 on success, -1 on error Creates an interrupt controller model in the kernel. On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both PIC and IOAPIC; GSI 16-23 only go to the IOAPIC. On ia64, a IOSAPIC is created. 4.25 KVM_IRQ_LINE Capability: KVM_CAP_IRQCHIP Architectures: x86, ia64 Type: vm ioctl Parameters: struct kvm_irq_level Returns: 0 on success, -1 on error Sets the level of a GSI input to the interrupt controller model in the kernel. Requires that an interrupt controller model has been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered interrupts require the level to be set to 1 and then back to 0. struct kvm_irq_level { union { __u32 irq; /* GSI */ __s32 status; /* not used for KVM_IRQ_LEVEL */ }; __u32 level; /* 0 or 1 */ }; 4.26 KVM_GET_IRQCHIP Capability: KVM_CAP_IRQCHIP Architectures: x86, ia64 Type: vm ioctl Parameters: struct kvm_irqchip (in/out) Returns: 0 on success, -1 on error Reads the state of a kernel interrupt controller created with KVM_CREATE_IRQCHIP into a buffer provided by the caller. struct kvm_irqchip { __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */ __u32 pad; union { char dummy[512]; /* reserving space */ struct kvm_pic_state pic; struct kvm_ioapic_state ioapic; } chip; }; 4.27 KVM_SET_IRQCHIP Capability: KVM_CAP_IRQCHIP Architectures: x86, ia64 Type: vm ioctl Parameters: struct kvm_irqchip (in) Returns: 0 on success, -1 on error Sets the state of a kernel interrupt controller created with KVM_CREATE_IRQCHIP from a buffer provided by the caller. struct kvm_irqchip { __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */ __u32 pad; union { char dummy[512]; /* reserving space */ struct kvm_pic_state pic; struct kvm_ioapic_state ioapic; } chip; }; 4.28 KVM_XEN_HVM_CONFIG Capability: KVM_CAP_XEN_HVM Architectures: x86 Type: vm ioctl Parameters: struct kvm_xen_hvm_config (in) Returns: 0 on success, -1 on error Sets the MSR that the Xen HVM guest uses to initialize its hypercall page, and provides the starting address and size of the hypercall blobs in userspace. When the guest writes the MSR, kvm copies one page of a blob (32- or 64-bit, depending on the vcpu mode) to guest memory. struct kvm_xen_hvm_config { __u32 flags; __u32 msr; __u64 blob_addr_32; __u64 blob_addr_64; __u8 blob_size_32; __u8 blob_size_64; __u8 pad2[30]; }; 4.29 KVM_GET_CLOCK Capability: KVM_CAP_ADJUST_CLOCK Architectures: x86 Type: vm ioctl Parameters: struct kvm_clock_data (out) Returns: 0 on success, -1 on error Gets the current timestamp of kvmclock as seen by the current guest. In conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; __u32 pad[9]; }; 4.30 KVM_SET_CLOCK Capability: KVM_CAP_ADJUST_CLOCK Architectures: x86 Type: vm ioctl Parameters: struct kvm_clock_data (in) Returns: 0 on success, -1 on error Sets the current timestamp of kvmclock to the value specified in its parameter. In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; __u32 pad[9]; }; 4.31 KVM_GET_VCPU_EVENTS Capability: KVM_CAP_VCPU_EVENTS Extended by: KVM_CAP_INTR_SHADOW Architectures: x86 Type: vm ioctl Parameters: struct kvm_vcpu_event (out) Returns: 0 on success, -1 on error Gets currently pending exceptions, interrupts, and NMIs as well as related states of the vcpu. struct kvm_vcpu_events { struct { __u8 injected; __u8 nr; __u8 has_error_code; __u8 pad; __u32 error_code; } exception; struct { __u8 injected; __u8 nr; __u8 soft; __u8 shadow; } interrupt; struct { __u8 injected; __u8 pending; __u8 masked; __u8 pad; } nmi; __u32 sipi_vector; __u32 flags; }; KVM_VCPUEVENT_VALID_SHADOW may be set in the flags field to signal that interrupt.shadow contains a valid state. Otherwise, this field is undefined. 4.32 KVM_SET_VCPU_EVENTS Capability: KVM_CAP_VCPU_EVENTS Extended by: KVM_CAP_INTR_SHADOW Architectures: x86 Type: vm ioctl Parameters: struct kvm_vcpu_event (in) Returns: 0 on success, -1 on error Set pending exceptions, interrupts, and NMIs as well as related states of the vcpu. See KVM_GET_VCPU_EVENTS for the data structure. Fields that may be modified asynchronously by running VCPUs can be excluded from the update. These fields are nmi.pending and sipi_vector. Keep the corresponding bits in the flags field cleared to suppress overwriting the current in-kernel state. The bits are: KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in the flags field to signal that interrupt.shadow contains a valid state and shall be written into the VCPU. 4.33 KVM_GET_DEBUGREGS Capability: KVM_CAP_DEBUGREGS Architectures: x86 Type: vm ioctl Parameters: struct kvm_debugregs (out) Returns: 0 on success, -1 on error Reads debug registers from the vcpu. struct kvm_debugregs { __u64 db[4]; __u64 dr6; __u64 dr7; __u64 flags; __u64 reserved[9]; }; 4.34 KVM_SET_DEBUGREGS Capability: KVM_CAP_DEBUGREGS Architectures: x86 Type: vm ioctl Parameters: struct kvm_debugregs (in) Returns: 0 on success, -1 on error Writes debug registers into the vcpu. See KVM_GET_DEBUGREGS for the data structure. The flags field is unused yet and must be cleared on entry. 4.35 KVM_SET_USER_MEMORY_REGION Capability: KVM_CAP_USER_MEM Architectures: all Type: vm ioctl Parameters: struct kvm_userspace_memory_region (in) Returns: 0 on success, -1 on error struct kvm_userspace_memory_region { __u32 slot; __u32 flags; __u64 guest_phys_addr; __u64 memory_size; /* bytes */ __u64 userspace_addr; /* start of the userspace allocated memory */ }; /* for kvm_memory_region::flags */ #define KVM_MEM_LOG_DIRTY_PAGES 1UL This ioctl allows the user to create or modify a guest physical memory slot. When changing an existing slot, it may be moved in the guest physical memory space, or its flags may be modified. It may not be resized. Slots may not overlap in guest physical address space. Memory for the region is taken starting at the address denoted by the field userspace_addr, which must point at user addressable memory for the entire memory slot size. Any object may back this memory, including anonymous memory, ordinary files, and hugetlbfs. It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr be identical. This allows large pages in the guest to be backed by large pages in the host. The flags field supports just one flag, KVM_MEM_LOG_DIRTY_PAGES, which instructs kvm to keep track of writes to memory within the slot. See the KVM_GET_DIRTY_LOG ioctl. When the KVM_CAP_SYNC_MMU capability, changes in the backing of the memory region are automatically reflected into the guest. For example, an mmap() that affects the region will be made visible immediately. Another example is madvise(MADV_DROP). It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl. The KVM_SET_MEMORY_REGION does not allow fine grained control over memory allocation and is deprecated. 4.36 KVM_SET_TSS_ADDR Capability: KVM_CAP_SET_TSS_ADDR Architectures: x86 Type: vm ioctl Parameters: unsigned long tss_address (in) Returns: 0 on success, -1 on error This ioctl defines the physical address of a three-page region in the guest physical address space. The region must be within the first 4GB of the guest physical address space and must not conflict with any memory slot or any mmio address. The guest may malfunction if it accesses this memory region. This ioctl is required on Intel-based hosts. This is needed on Intel hardware because of a quirk in the virtualization implementation (see the internals documentation when it pops into existence). 4.37 KVM_ENABLE_CAP Capability: KVM_CAP_ENABLE_CAP Architectures: ppc Type: vcpu ioctl Parameters: struct kvm_enable_cap (in) Returns: 0 on success; -1 on error +Not all extensions are enabled by default. Using this ioctl the application can enable an extension, making it available to the guest. On systems that do not support this ioctl, it always fails. On systems that do support it, it only works for extensions that are supported for enablement. To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should be used. struct kvm_enable_cap { /* in */ __u32 cap; The capability that is supposed to get enabled. __u32 flags; A bitfield indicating future enhancements. Has to be 0 for now. __u64 args[4]; Arguments for enabling a feature. If a feature needs initial values to function properly, this is the place to put them. __u8 pad[64]; }; 4.38 KVM_GET_MP_STATE Capability: KVM_CAP_MP_STATE Architectures: x86, ia64 Type: vcpu ioctl Parameters: struct kvm_mp_state (out) Returns: 0 on success; -1 on error struct kvm_mp_state { __u32 mp_state; }; Returns the vcpu's current "multiprocessing state" (though also valid on uniprocessor guests). Possible values are: - KVM_MP_STATE_RUNNABLE: the vcpu is currently running - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP) which has not yet received an INIT signal - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is now ready for a SIPI - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and is waiting for an interrupt - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector accessible via KVM_GET_VCPU_EVENTS) This ioctl is only useful after KVM_CREATE_IRQCHIP. Without an in-kernel irqchip, the multiprocessing state must be maintained by userspace. 4.39 KVM_SET_MP_STATE Capability: KVM_CAP_MP_STATE Architectures: x86, ia64 Type: vcpu ioctl Parameters: struct kvm_mp_state (in) Returns: 0 on success; -1 on error Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for arguments. This ioctl is only useful after KVM_CREATE_IRQCHIP. Without an in-kernel irqchip, the multiprocessing state must be maintained by userspace. 4.40 KVM_SET_IDENTITY_MAP_ADDR Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR Architectures: x86 Type: vm ioctl Parameters: unsigned long identity (in) Returns: 0 on success, -1 on error This ioctl defines the physical address of a one-page region in the guest physical address space. The region must be within the first 4GB of the guest physical address space and must not conflict with any memory slot or any mmio address. The guest may malfunction if it accesses this memory region. This ioctl is required on Intel-based hosts. This is needed on Intel hardware because of a quirk in the virtualization implementation (see the internals documentation when it pops into existence). 4.41 KVM_SET_BOOT_CPU_ID Capability: KVM_CAP_SET_BOOT_CPU_ID Architectures: x86, ia64 Type: vm ioctl Parameters: unsigned long vcpu_id Returns: 0 on success, -1 on error Define which vcpu is the Bootstrap Processor (BSP). Values are the same as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default is vcpu 0. 4.42 KVM_GET_XSAVE Capability: KVM_CAP_XSAVE Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xsave (out) Returns: 0 on success, -1 on error struct kvm_xsave { __u32 region[1024]; }; This ioctl would copy current vcpu's xsave struct to the userspace. 4.43 KVM_SET_XSAVE Capability: KVM_CAP_XSAVE Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xsave (in) Returns: 0 on success, -1 on error struct kvm_xsave { __u32 region[1024]; }; This ioctl would copy userspace's xsave struct to the kernel. 4.44 KVM_GET_XCRS Capability: KVM_CAP_XCRS Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xcrs (out) Returns: 0 on success, -1 on error struct kvm_xcr { __u32 xcr; __u32 reserved; __u64 value; }; struct kvm_xcrs { __u32 nr_xcrs; __u32 flags; struct kvm_xcr xcrs[KVM_MAX_XCRS]; __u64 padding[16]; }; This ioctl would copy current vcpu's xcrs to the userspace. 4.45 KVM_SET_XCRS Capability: KVM_CAP_XCRS Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xcrs (in) Returns: 0 on success, -1 on error struct kvm_xcr { __u32 xcr; __u32 reserved; __u64 value; }; struct kvm_xcrs { __u32 nr_xcrs; __u32 flags; struct kvm_xcr xcrs[KVM_MAX_XCRS]; __u64 padding[16]; }; This ioctl would set vcpu's xcr to the value userspace specified. 4.46 KVM_GET_SUPPORTED_CPUID Capability: KVM_CAP_EXT_CPUID Architectures: x86 Type: system ioctl Parameters: struct kvm_cpuid2 (in/out) Returns: 0 on success, -1 on error struct kvm_cpuid2 { __u32 nent; __u32 padding; struct kvm_cpuid_entry2 entries[0]; }; #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX 1 #define KVM_CPUID_FLAG_STATEFUL_FUNC 2 #define KVM_CPUID_FLAG_STATE_READ_NEXT 4 struct kvm_cpuid_entry2 { __u32 function; __u32 index; __u32 flags; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding[3]; }; This ioctl returns x86 cpuid features which are supported by both the hardware and kvm. Userspace can use the information returned by this ioctl to construct cpuid information (for KVM_SET_CPUID2) that is consistent with hardware, kernel, and userspace capabilities, and with user requirements (for example, the user may wish to constrain cpuid to emulate older hardware, or for feature consistency across a cluster). Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure with the 'nent' field indicating the number of entries in the variable-size array 'entries'. If the number of entries is too low to describe the cpu capabilities, an error (E2BIG) is returned. If the number is too high, the 'nent' field is adjusted and an error (ENOMEM) is returned. If the number is just right, the 'nent' field is adjusted to the number of valid entries in the 'entries' array, which is then filled. The entries returned are the host cpuid as returned by the cpuid instruction, with unknown or unsupported features masked out. Some features (for example, x2apic), may not be present in the host cpu, but are exposed by kvm if it can emulate them efficiently. The fields in each entry are defined as follows: function: the eax value used to obtain the entry index: the ecx value used to obtain the entry (for entries that are affected by ecx) flags: an OR of zero or more of the following: KVM_CPUID_FLAG_SIGNIFCANT_INDEX: if the index field is valid KVM_CPUID_FLAG_STATEFUL_FUNC: if cpuid for this function returns different values for successive invocations; there will be several entries with the same function, all with this flag set KVM_CPUID_FLAG_STATE_READ_NEXT: for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is the first entry to be read by a cpu eax, ebx, ecx, edx: the values returned by the cpuid instruction for this function/index combination The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC support. Instead it is reported via ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER) if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the feature in userspace, then you can enable the feature for KVM_SET_CPUID2. 4.47 KVM_PPC_GET_PVINFO Capability: KVM_CAP_PPC_GET_PVINFO Architectures: ppc Type: vm ioctl Parameters: struct kvm_ppc_pvinfo (out) Returns: 0 on success, !0 on error struct kvm_ppc_pvinfo { __u32 flags; __u32 hcall[4]; __u8 pad[108]; }; This ioctl fetches PV specific information that need to be passed to the guest using the device tree or other means from vm context. For now the only implemented piece of information distributed here is an array of 4 instructions that make up a hypercall. If any additional field gets added to this structure later on, a bit for that additional piece of information will be set in the flags bitmap. 4.48 KVM_ASSIGN_PCI_DEVICE Capability: KVM_CAP_DEVICE_ASSIGNMENT Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_pci_dev (in) Returns: 0 on success, -1 on error Assigns a host PCI device to the VM. struct kvm_assigned_pci_dev { __u32 assigned_dev_id; __u32 busnr; __u32 devfn; __u32 flags; __u32 segnr; union { __u32 reserved[11]; }; }; The PCI device is specified by the triple segnr, busnr, and devfn. Identification in succeeding service requests is done via assigned_dev_id. The following flags are specified: /* Depends on KVM_CAP_IOMMU */ #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) The KVM_DEV_ASSIGN_ENABLE_IOMMU flag is a mandatory option to ensure isolation of the device. Usages not specifying this flag are deprecated. Only PCI header type 0 devices with PCI BAR resources are supported by device assignment. The user requesting this ioctl must have read/write access to the PCI sysfs resource files associated with the device. 4.49 KVM_DEASSIGN_PCI_DEVICE Capability: KVM_CAP_DEVICE_DEASSIGNMENT Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_pci_dev (in) Returns: 0 on success, -1 on error Ends PCI device assignment, releasing all associated resources. See KVM_CAP_DEVICE_ASSIGNMENT for the data structure. Only assigned_dev_id is used in kvm_assigned_pci_dev to identify the device. 4.50 KVM_ASSIGN_DEV_IRQ Capability: KVM_CAP_ASSIGN_DEV_IRQ Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_irq (in) Returns: 0 on success, -1 on error Assigns an IRQ to a passed-through device. struct kvm_assigned_irq { __u32 assigned_dev_id; __u32 host_irq; /* ignored (legacy field) */ __u32 guest_irq; __u32 flags; union { __u32 reserved[12]; }; }; The following flags are defined: #define KVM_DEV_IRQ_HOST_INTX (1 << 0) #define KVM_DEV_IRQ_HOST_MSI (1 << 1) #define KVM_DEV_IRQ_HOST_MSIX (1 << 2) #define KVM_DEV_IRQ_GUEST_INTX (1 << 8) #define KVM_DEV_IRQ_GUEST_MSI (1 << 9) #define KVM_DEV_IRQ_GUEST_MSIX (1 << 10) It is not valid to specify multiple types per host or guest IRQ. However, the IRQ type of host and guest can differ or can even be null. 4.51 KVM_DEASSIGN_DEV_IRQ Capability: KVM_CAP_ASSIGN_DEV_IRQ Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_irq (in) Returns: 0 on success, -1 on error Ends an IRQ assignment to a passed-through device. See KVM_ASSIGN_DEV_IRQ for the data structure. The target device is specified by assigned_dev_id, flags must correspond to the IRQ type specified on KVM_ASSIGN_DEV_IRQ. Partial deassignment of host or guest IRQ is allowed. 4.52 KVM_SET_GSI_ROUTING Capability: KVM_CAP_IRQ_ROUTING Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_irq_routing (in) Returns: 0 on success, -1 on error Sets the GSI routing table entries, overwriting any previously set entries. struct kvm_irq_routing { __u32 nr; __u32 flags; struct kvm_irq_routing_entry entries[0]; }; No flags are specified so far, the corresponding field must be set to zero. struct kvm_irq_routing_entry { __u32 gsi; __u32 type; __u32 flags; __u32 pad; union { struct kvm_irq_routing_irqchip irqchip; struct kvm_irq_routing_msi msi; __u32 pad[8]; } u; }; /* gsi routing entry types */ #define KVM_IRQ_ROUTING_IRQCHIP 1 #define KVM_IRQ_ROUTING_MSI 2 No flags are specified so far, the corresponding field must be set to zero. struct kvm_irq_routing_irqchip { __u32 irqchip; __u32 pin; }; struct kvm_irq_routing_msi { __u32 address_lo; __u32 address_hi; __u32 data; __u32 pad; }; 4.53 KVM_ASSIGN_SET_MSIX_NR Capability: KVM_CAP_DEVICE_MSIX Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_msix_nr (in) Returns: 0 on success, -1 on error Set the number of MSI-X interrupts for an assigned device. The number is reset again by terminating the MSI-X assignment of the device via KVM_DEASSIGN_DEV_IRQ. Calling this service more than once at any earlier point will fail. struct kvm_assigned_msix_nr { __u32 assigned_dev_id; __u16 entry_nr; __u16 padding; }; #define KVM_MAX_MSIX_PER_DEV 256 4.54 KVM_ASSIGN_SET_MSIX_ENTRY Capability: KVM_CAP_DEVICE_MSIX Architectures: x86 ia64 Type: vm ioctl Parameters: struct kvm_assigned_msix_entry (in) Returns: 0 on success, -1 on error Specifies the routing of an MSI-X assigned device interrupt to a GSI. Setting the GSI vector to zero means disabling the interrupt. struct kvm_assigned_msix_entry { __u32 assigned_dev_id; __u32 gsi; __u16 entry; /* The index of entry in the MSI-X table */ __u16 padding[3]; }; 4.54 KVM_SET_TSC_KHZ Capability: KVM_CAP_TSC_CONTROL Architectures: x86 Type: vcpu ioctl Parameters: virtual tsc_khz Returns: 0 on success, -1 on error Specifies the tsc frequency for the virtual machine. The unit of the frequency is KHz. 4.55 KVM_GET_TSC_KHZ Capability: KVM_CAP_GET_TSC_KHZ Architectures: x86 Type: vcpu ioctl Parameters: none Returns: virtual tsc-khz on success, negative value on error Returns the tsc frequency of the guest. The unit of the return value is KHz. If the host has unstable tsc this ioctl returns -EIO instead as an error. 4.56 KVM_GET_LAPIC Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_lapic_state (out) Returns: 0 on success, -1 on error #define KVM_APIC_REG_SIZE 0x400 struct kvm_lapic_state { char regs[KVM_APIC_REG_SIZE]; }; Reads the Local APIC registers and copies them into the input argument. The data format and layout are the same as documented in the architecture manual. 4.57 KVM_SET_LAPIC Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_lapic_state (in) Returns: 0 on success, -1 on error #define KVM_APIC_REG_SIZE 0x400 struct kvm_lapic_state { char regs[KVM_APIC_REG_SIZE]; }; Copies the input argument into the the Local APIC registers. The data format and layout are the same as documented in the architecture manual. 4.58 KVM_IOEVENTFD Capability: KVM_CAP_IOEVENTFD Architectures: all Type: vm ioctl Parameters: struct kvm_ioeventfd (in) Returns: 0 on success, !0 on error This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address within the guest. A guest write in the registered address will signal the provided event instead of triggering an exit. struct kvm_ioeventfd { __u64 datamatch; __u64 addr; /* legal pio/mmio address */ __u32 len; /* 1, 2, 4, or 8 bytes */ __s32 fd; __u32 flags; __u8 pad[36]; }; The following flags are defined: #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch) #define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio) #define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign) If datamatch flag is set, the event will be signaled only if the written value to the registered address is equal to datamatch in struct kvm_ioeventfd. 4.62 KVM_CREATE_SPAPR_TCE Capability: KVM_CAP_SPAPR_TCE Architectures: powerpc Type: vm ioctl Parameters: struct kvm_create_spapr_tce (in) Returns: file descriptor for manipulating the created TCE table This creates a virtual TCE (translation control entry) table, which is an IOMMU for PAPR-style virtual I/O. It is used to translate logical addresses used in virtual I/O into guest physical addresses, and provides a scatter/gather capability for PAPR virtual I/O. /* for KVM_CAP_SPAPR_TCE */ struct kvm_create_spapr_tce { __u64 liobn; __u32 window_size; }; The liobn field gives the logical IO bus number for which to create a TCE table. The window_size field specifies the size of the DMA window which this TCE table will translate - the table will contain one 64 bit TCE entry for every 4kiB of the DMA window. When the guest issues an H_PUT_TCE hcall on a liobn for which a TCE table has been created using this ioctl(), the kernel will handle it in real mode, updating the TCE table. H_PUT_TCE calls for other liobns will cause a vm exit and must be handled by userspace. The return value is a file descriptor which can be passed to mmap(2) to map the created TCE table into userspace. This lets userspace read the entries written by kernel-handled H_PUT_TCE calls, and also lets userspace update the TCE table directly which is useful in some circumstances. 4.63 KVM_ALLOCATE_RMA Capability: KVM_CAP_PPC_RMA Architectures: powerpc Type: vm ioctl Parameters: struct kvm_allocate_rma (out) Returns: file descriptor for mapping the allocated RMA This allocates a Real Mode Area (RMA) from the pool allocated at boot time by the kernel. An RMA is a physically-contiguous, aligned region of memory used on older POWER processors to provide the memory which will be accessed by real-mode (MMU off) accesses in a KVM guest. POWER processors support a set of sizes for the RMA that usually includes 64MB, 128MB, 256MB and some larger powers of two. /* for KVM_ALLOCATE_RMA */ struct kvm_allocate_rma { __u64 rma_size; }; The return value is a file descriptor which can be passed to mmap(2) to map the allocated RMA into userspace. The mapped area can then be passed to the KVM_SET_USER_MEMORY_REGION ioctl to establish it as the RMA for a virtual machine. The size of the RMA in bytes (which is fixed at host kernel boot time) is returned in the rma_size field of the argument structure. The KVM_CAP_PPC_RMA capability is 1 or 2 if the KVM_ALLOCATE_RMA ioctl is supported; 2 if the processor requires all virtual machines to have an RMA, or 1 if the processor can use an RMA but doesn't require it, because it supports the Virtual RMA (VRMA) facility. 4.64 KVM_NMI Capability: KVM_CAP_USER_NMI Architectures: x86 Type: vcpu ioctl Parameters: none Returns: 0 on success, -1 on error Queues an NMI on the thread's vcpu. Note this is well defined only when KVM_CREATE_IRQCHIP has not been called, since this is an interface between the virtual cpu core and virtual local APIC. After KVM_CREATE_IRQCHIP has been called, this interface is completely emulated within the kernel. To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the following algorithm: - pause the vpcu - read the local APIC's state (KVM_GET_LAPIC) - check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1) - if so, issue KVM_NMI - resume the vcpu Some guests configure the LINT1 NMI input to cause a panic, aiding in debugging. 5. The kvm_run structure Application code obtains a pointer to the kvm_run structure by mmap()ing a vcpu fd. From that point, application code can control execution by changing fields in kvm_run prior to calling the KVM_RUN ioctl, and obtain information about the reason KVM_RUN returned by looking up structure members. struct kvm_run { /* in */ __u8 request_interrupt_window; Request that KVM_RUN return when it becomes possible to inject external interrupts into the guest. Useful in conjunction with KVM_INTERRUPT. __u8 padding1[7]; /* out */ __u32 exit_reason; When KVM_RUN has returned successfully (return value 0), this informs application code why KVM_RUN has returned. Allowable values for this field are detailed below. __u8 ready_for_interrupt_injection; If request_interrupt_window has been specified, this field indicates an interrupt can be injected now with KVM_INTERRUPT. __u8 if_flag; The value of the current interrupt flag. Only valid if in-kernel local APIC is not used. __u8 padding2[2]; /* in (pre_kvm_run), out (post_kvm_run) */ __u64 cr8; The value of the cr8 register. Only valid if in-kernel local APIC is not used. Both input and output. __u64 apic_base; The value of the APIC BASE msr. Only valid if in-kernel local APIC is not used. Both input and output. union { /* KVM_EXIT_UNKNOWN */ struct { __u64 hardware_exit_reason; } hw; If exit_reason is KVM_EXIT_UNKNOWN, the vcpu has exited due to unknown reasons. Further architecture-specific information is available in hardware_exit_reason. /* KVM_EXIT_FAIL_ENTRY */ struct { __u64 hardware_entry_failure_reason; } fail_entry; If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due to unknown reasons. Further architecture-specific information is available in hardware_entry_failure_reason. /* KVM_EXIT_EXCEPTION */ struct { __u32 exception; __u32 error_code; } ex; Unused. /* KVM_EXIT_IO */ struct { #define KVM_EXIT_IO_IN 0 #define KVM_EXIT_IO_OUT 1 __u8 direction; __u8 size; /* bytes */ __u16 port; __u32 count; __u64 data_offset; /* relative to kvm_run start */ } io; If exit_reason is KVM_EXIT_IO, then the vcpu has executed a port I/O instruction which could not be satisfied by kvm. data_offset describes where the data is located (KVM_EXIT_IO_OUT) or where kvm expects application code to place the data for the next KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array. struct { struct kvm_debug_exit_arch arch; } debug; Unused. /* KVM_EXIT_MMIO */ struct { __u64 phys_addr; __u8 data[8]; __u32 len; __u8 is_write; } mmio; If exit_reason is KVM_EXIT_MMIO, then the vcpu has executed a memory-mapped I/O instruction which could not be satisfied by kvm. The 'data' member contains the written data if 'is_write' is true, and should be filled by application code otherwise. NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO and KVM_EXIT_OSI, the corresponding operations are complete (and guest state is consistent) only after userspace has re-entered the kernel with KVM_RUN. The kernel side will first finish incomplete operations and then check for pending signals. Userspace can re-enter the guest with an unmasked signal pending to complete pending operations. /* KVM_EXIT_HYPERCALL */ struct { __u64 nr; __u64 args[6]; __u64 ret; __u32 longmode; __u32 pad; } hypercall; Unused. This was once used for 'hypercall to userspace'. To implement such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390). Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO. /* KVM_EXIT_TPR_ACCESS */ struct { __u64 rip; __u32 is_write; __u32 pad; } tpr_access; To be documented (KVM_TPR_ACCESS_REPORTING). /* KVM_EXIT_S390_SIEIC */ struct { __u8 icptcode; __u64 mask; /* psw upper half */ __u64 addr; /* psw lower half */ __u16 ipa; __u32 ipb; } s390_sieic; s390 specific. /* KVM_EXIT_S390_RESET */ #define KVM_S390_RESET_POR 1 #define KVM_S390_RESET_CLEAR 2 #define KVM_S390_RESET_SUBSYSTEM 4 #define KVM_S390_RESET_CPU_INIT 8 #define KVM_S390_RESET_IPL 16 __u64 s390_reset_flags; s390 specific. /* KVM_EXIT_DCR */ struct { __u32 dcrn; __u32 data; __u8 is_write; } dcr; powerpc specific. /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; } osi; MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch hypercalls and exit with this exit struct that contains all the guest gprs. If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall. Userspace can now handle the hypercall and when it's done modify the gprs as necessary. Upon guest entry all guest GPRs will then be replaced by the values in this struct. /* KVM_EXIT_PAPR_HCALL */ struct { __u64 nr; __u64 ret; __u64 args[9]; } papr_hcall; This is used on 64-bit PowerPC when emulating a pSeries partition, e.g. with the 'pseries' machine type in qemu. It occurs when the guest does a hypercall using the 'sc 1' instruction. The 'nr' field contains the hypercall number (from the guest R3), and 'args' contains the arguments (from the guest R4 - R12). Userspace should put the return code in 'ret' and any extra returned values in args[]. The possible hypercalls are defined in the Power Architecture Platform Requirements (PAPR) document available from www.power.org (free developer registration required to access it). /* Fix the size of the union. */ char padding[256]; }; }; 6. Capabilities that can be enabled There are certain capabilities that change the behavior of the virtual CPU when enabled. To enable them, please see section 4.37. Below you can find a list of capabilities and what their effect on the vCPU is when enabling them. The following information is provided along with the description: Architectures: which instruction set architectures provide this ioctl. x86 includes both i386 and x86_64. Parameters: what parameters are accepted by the capability. Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL) are not detailed, but errors with specific meanings are. 6.1 KVM_CAP_PPC_OSI Architectures: ppc Parameters: none Returns: 0 on success; -1 on error This capability enables interception of OSI hypercalls that otherwise would be treated as normal system calls to be injected into the guest. OSI hypercalls were invented by Mac-on-Linux to have a standardized communication mechanism between the guest and the host. When this capability is enabled, KVM_EXIT_OSI can occur. 6.2 KVM_CAP_PPC_PAPR Architectures: ppc Parameters: none Returns: 0 on success; -1 on error This capability enables interception of PAPR hypercalls. PAPR hypercalls are done using the hypercall instruction "sc 1". It also sets the guest privilege level to "supervisor" mode. Usually the guest runs in "hypervisor" privilege mode with a few missing features. In addition to the above, it changes the semantics of SDR1. In this mode, the HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the HTAB invisible to the guest. When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur.