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Diffstat (limited to 'Documentation/virt/kvm/api.rst')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 118 |
1 files changed, 109 insertions, 9 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 85c7abc51af5..47c483d440f3 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1476,14 +1476,43 @@ Possible values are: [s390] KVM_MP_STATE_LOAD the vcpu is in a special load/startup state [s390] + KVM_MP_STATE_SUSPENDED the vcpu is in a suspend state and is waiting + for a wakeup event [arm64] ========================== =============================================== On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an in-kernel irqchip, the multiprocessing state must be maintained by userspace on these architectures. -For arm64/riscv: -^^^^^^^^^^^^^^^^ +For arm64: +^^^^^^^^^^ + +If a vCPU is in the KVM_MP_STATE_SUSPENDED state, KVM will emulate the +architectural execution of a WFI instruction. + +If a wakeup event is recognized, KVM will exit to userspace with a +KVM_SYSTEM_EVENT exit, where the event type is KVM_SYSTEM_EVENT_WAKEUP. If +userspace wants to honor the wakeup, it must set the vCPU's MP state to +KVM_MP_STATE_RUNNABLE. If it does not, KVM will continue to await a wakeup +event in subsequent calls to KVM_RUN. + +.. warning:: + + If userspace intends to keep the vCPU in a SUSPENDED state, it is + strongly recommended that userspace take action to suppress the + wakeup event (such as masking an interrupt). Otherwise, subsequent + calls to KVM_RUN will immediately exit with a KVM_SYSTEM_EVENT_WAKEUP + event and inadvertently waste CPU cycles. + + Additionally, if userspace takes action to suppress a wakeup event, + it is strongly recommended that it also restores the vCPU to its + original state when the vCPU is made RUNNABLE again. For example, + if userspace masked a pending interrupt to suppress the wakeup, + the interrupt should be unmasked before returning control to the + guest. + +For riscv: +^^^^^^^^^^ The only states that are valid are KVM_MP_STATE_STOPPED and KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not. @@ -2601,6 +2630,24 @@ EINVAL. After the vcpu's SVE configuration is finalized, further attempts to write this register will fail with EPERM. +arm64 bitmap feature firmware pseudo-registers have the following bit pattern:: + + 0x6030 0000 0016 <regno:16> + +The bitmap feature firmware registers exposes the hypercall services that +are available for userspace to configure. The set bits corresponds to the +services that are available for the guests to access. By default, KVM +sets all the supported bits during VM initialization. The userspace can +discover the available services via KVM_GET_ONE_REG, and write back the +bitmap corresponding to the features that it wishes guests to see via +KVM_SET_ONE_REG. + +Note: These registers are immutable once any of the vCPUs of the VM has +run at least once. A KVM_SET_ONE_REG in such a scenario will return +a -EBUSY to userspace. + +(See Documentation/virt/kvm/arm/hypercalls.rst for more details.) + MIPS registers are mapped using the lower 32 bits. The upper 16 of that is the register group type: @@ -5985,17 +6032,19 @@ should put the acknowledged interrupt vector into the 'epr' field. #define KVM_SYSTEM_EVENT_SHUTDOWN 1 #define KVM_SYSTEM_EVENT_RESET 2 #define KVM_SYSTEM_EVENT_CRASH 3 + #define KVM_SYSTEM_EVENT_WAKEUP 4 + #define KVM_SYSTEM_EVENT_SUSPEND 5 __u32 type; - __u64 flags; + __u32 ndata; + __u64 data[16]; } system_event; If exit_reason is KVM_EXIT_SYSTEM_EVENT then the vcpu has triggered a system-level event using some architecture specific mechanism (hypercall or some special instruction). In case of ARM64, this is triggered using -HVC instruction based PSCI call from the vcpu. The 'type' field describes -the system-level event type. The 'flags' field describes architecture -specific flags for the system-level event. +HVC instruction based PSCI call from the vcpu. +The 'type' field describes the system-level event type. Valid values for 'type' are: - KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the @@ -6009,11 +6058,52 @@ Valid values for 'type' are: has requested a crash condition maintenance. Userspace can choose to ignore the request, or to gather VM memory core dump and/or reset/shutdown of the VM. + - KVM_SYSTEM_EVENT_WAKEUP -- the exiting vCPU is in a suspended state and + KVM has recognized a wakeup event. Userspace may honor this event by + marking the exiting vCPU as runnable, or deny it and call KVM_RUN again. + - KVM_SYSTEM_EVENT_SUSPEND -- the guest has requested a suspension of + the VM. -Valid flags are: +For arm/arm64: +-------------- - - KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2 (arm64 only) -- the guest issued - a SYSTEM_RESET2 call according to v1.1 of the PSCI specification. + KVM_SYSTEM_EVENT_SUSPEND exits are enabled with the + KVM_CAP_ARM_SYSTEM_SUSPEND VM capability. If a guest invokes the PSCI + SYSTEM_SUSPEND function, KVM will exit to userspace with this event + type. + + It is the sole responsibility of userspace to implement the PSCI + SYSTEM_SUSPEND call according to ARM DEN0022D.b 5.19 "SYSTEM_SUSPEND". + KVM does not change the vCPU's state before exiting to userspace, so + the call parameters are left in-place in the vCPU registers. + + Userspace is _required_ to take action for such an exit. It must + either: + + - Honor the guest request to suspend the VM. Userspace can request + in-kernel emulation of suspension by setting the calling vCPU's + state to KVM_MP_STATE_SUSPENDED. Userspace must configure the vCPU's + state according to the parameters passed to the PSCI function when + the calling vCPU is resumed. See ARM DEN0022D.b 5.19.1 "Intended use" + for details on the function parameters. + + - Deny the guest request to suspend the VM. See ARM DEN0022D.b 5.19.2 + "Caller responsibilities" for possible return values. + +If KVM_CAP_SYSTEM_EVENT_DATA is present, the 'data' field can contain +architecture specific information for the system-level event. Only +the first `ndata` items (possibly zero) of the data array are valid. + + - for arm64, data[0] is set to KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2 if + the guest issued a SYSTEM_RESET2 call according to v1.1 of the PSCI + specification. + + - for RISC-V, data[0] is set to the value of the second argument of the + ``sbi_system_reset`` call. + +Previous versions of Linux defined a `flags` member in this struct. The +field is now aliased to `data[0]`. Userspace can assume that it is only +written if ndata is greater than 0. :: @@ -7724,6 +7814,16 @@ At this time, KVM_PMU_CAP_DISABLE is the only capability. Setting this capability will disable PMU virtualization for that VM. Usermode should adjust CPUID leaf 0xA to reflect that the PMU is disabled. +8.36 KVM_CAP_ARM_SYSTEM_SUSPEND +------------------------------- + +:Capability: KVM_CAP_ARM_SYSTEM_SUSPEND +:Architectures: arm64 +:Type: vm + +When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of +type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request. + 9. Known KVM API problems ========================= |