Add brief documentation for KVM_CAP_X86_NOTIFY_VMEXIT, as well as the new field in kvm_run struct for the exit reason KVM_EXIT_NOTIFY. Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx> --- Documentation/virt/kvm/api.rst | 39 ++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9682b0a438bd..d60b03b5a63e 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6199,6 +6199,26 @@ array field represents return values. The userspace should update the return values of SBI call before resuming the VCPU. For more details on RISC-V SBI spec refer, https://github.com/riscv/riscv-sbi-doc. +:: + + /* KVM_EXIT_NOTIFY */ + struct { + #define KVM_NOTIFY_CONTEXT_INVALID (1 << 0) + __u32 data; + } notify; + +Used on x86 systems. When the VM capability KVM_CAP_X86_NOTIFY_VMEXIT is +enabled and the parameter is non-negative, a VM exit generated if no event +window occurs in VM non-root mode for a specified amount of time. In some +special case, e.g. VM context invalid, it should exit to userspace with the +exit reason KVM_EXIT_NOTIFY for further handling. The "data" field contains +the more detailed info. + +Valid values for 'data' are: + + - KVM_NOTIFY_CONTEXT_INVALID -- the VM context is corrupted and not valid + in VMCS. It would run into unknown result if resume the target VM. + :: /* Fix the size of the union. */ @@ -7085,6 +7105,25 @@ resource that is controlled with the H_SET_MODE hypercall. This capability allows a guest kernel to use a better-performance mode for handling interrupts and system calls. +7.31 KVM_CAP_X86_NOTIFY_VMEXIT +------------------------------ + +:Architectures: x86 +:Target: VM +:Parameters: args[0] is the value of notify window +:Returns: 0 on success, -EINVAL if hardware doesn't support notify VM exit. + +This capability allows userspace to configure the notify VM exit on/off +in per-VM scope during VM creation. Notify VM exit is disabled by default. +When userspace provides a non-negative value in args[0], VMM would enable +this feature to trigger VM exit if no event window occurs in VM non-root +mode for a specified of time (notify window). The notify window is determined +by args[0]. + +This capability is aimed to mitigate the threat that malicious VMs can +cause CPU stuck (due to event windows don't open up) and make the CPU +unavailable to host or other VMs. + 8. Other capabilities. ====================== -- 2.17.1
