diff options
Diffstat (limited to 'Documentation/virt/kvm/api.txt')
| -rw-r--r-- | Documentation/virt/kvm/api.txt | 55 |
1 files changed, 54 insertions, 1 deletions
diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt index f94d06a12d20..49183add44e7 100644 --- a/Documentation/virt/kvm/api.txt +++ b/Documentation/virt/kvm/api.txt @@ -1002,12 +1002,18 @@ Specifying exception.has_esr on a system that does not support it will return -EINVAL. Setting anything other than the lower 24bits of exception.serror_esr will return -EINVAL. +It is not possible to read back a pending external abort (injected via +KVM_SET_VCPU_EVENTS or otherwise) because such an exception is always delivered +directly to the virtual CPU). + + struct kvm_vcpu_events { struct { __u8 serror_pending; __u8 serror_has_esr; + __u8 ext_dabt_pending; /* Align it to 8 bytes */ - __u8 pad[6]; + __u8 pad[5]; __u64 serror_esr; } exception; __u32 reserved[12]; @@ -1051,9 +1057,23 @@ contain a valid state and shall be written into the VCPU. ARM/ARM64: +User space may need to inject several types of events to the guest. + Set the pending SError exception state for this VCPU. It is not possible to 'cancel' an Serror that has been made pending. +If the guest performed an access to I/O memory which could not be handled by +userspace, for example because of missing instruction syndrome decode +information or because there is no device mapped at the accessed IPA, then +userspace can ask the kernel to inject an external abort using the address +from the exiting fault on the VCPU. It is a programming error to set +ext_dabt_pending after an exit which was not either KVM_EXIT_MMIO or +KVM_EXIT_ARM_NISV. This feature is only available if the system supports +KVM_CAP_ARM_INJECT_EXT_DABT. This is a helper which provides commonality in +how userspace reports accesses for the above cases to guests, across different +userspace implementations. Nevertheless, userspace can still emulate all Arm +exceptions by manipulating individual registers using the KVM_SET_ONE_REG API. + See KVM_GET_VCPU_EVENTS for the data structure. @@ -4471,6 +4491,39 @@ Hyper-V SynIC state change. Notification is used to remap SynIC event/message pages and to enable/disable SynIC messages/events processing in userspace. + /* KVM_EXIT_ARM_NISV */ + struct { + __u64 esr_iss; + __u64 fault_ipa; + } arm_nisv; + +Used on arm and arm64 systems. If a guest accesses memory not in a memslot, +KVM will typically return to userspace and ask it to do MMIO emulation on its +behalf. However, for certain classes of instructions, no instruction decode +(direction, length of memory access) is provided, and fetching and decoding +the instruction from the VM is overly complicated to live in the kernel. + +Historically, when this situation occurred, KVM would print a warning and kill +the VM. KVM assumed that if the guest accessed non-memslot memory, it was +trying to do I/O, which just couldn't be emulated, and the warning message was +phrased accordingly. However, what happened more often was that a guest bug +caused access outside the guest memory areas which should lead to a more +meaningful warning message and an external abort in the guest, if the access +did not fall within an I/O window. + +Userspace implementations can query for KVM_CAP_ARM_NISV_TO_USER, and enable +this capability at VM creation. Once this is done, these types of errors will +instead return to userspace with KVM_EXIT_ARM_NISV, with the valid bits from +the HSR (arm) and ESR_EL2 (arm64) in the esr_iss field, and the faulting IPA +in the fault_ipa field. Userspace can either fix up the access if it's +actually an I/O access by decoding the instruction from guest memory (if it's +very brave) and continue executing the guest, or it can decide to suspend, +dump, or restart the guest. + +Note that KVM does not skip the faulting instruction as it does for +KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state +if it decides to decode and emulate the instruction. + /* Fix the size of the union. */ char padding[256]; }; |