Signed-off-by: Peng Hao <[email protected]> --- Documentation/virtual/kvm/api.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 647f941..9615b9e 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -3676,6 +3676,30 @@ Returns: 0 on success, -1 on error This copies the vcpu's kvm_nested_state struct from userspace to the kernel. For the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE. +4.116 KVM_(UN)REGISTER_COALESCED_MMIO + +Capability: KVM_CAP_COALESCED_MMIO +Architectures: all +Type: vm ioctl +Parameters: struct kvm_coalesced_mmio_zone +Returns: 0 on success, < 0 on error + +Coalesced mmio is a performance optimization that defers hardware +register write emulation so that userspace exits are avoided. It is +typically used to reduce the overhead of emulating frequently accessed +hardware registers. + +When a hardware register is configured for coalesced mmio, write accesses +do not exit to userspace and their value is recorded in a shared coalesced +ring in the kernel. + +Coalesced mmio is applied to the following scenario typically. +If a write access to a hardware register can be deferred, following a +read/write access to another hardware register on the same device +will cause the shared coalesced ring to be processed by userspace +before emulating the current access. That will reduce the first write +access to userspace. + 5. The kvm_run structure ------------------------ -- 1.8.3.1
