Signed-off-by: Peng Hao <[email protected]> --- Documentation/virtual/kvm/api.txt | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 9615b9e..d3a0497 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -3678,18 +3678,19 @@ the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE. 4.116 KVM_(UN)REGISTER_COALESCED_MMIO -Capability: KVM_CAP_COALESCED_MMIO +Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio) + KVM_CAP_COALESCED_PIO (for coalesced pio) 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 +Coalesced I/O 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 +When a hardware register is configured for coalesced I/O, write accesses do not exit to userspace and their value is recorded in a shared coalesced ring in the kernel. @@ -3700,6 +3701,9 @@ 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. +Coalesced pio is based on coalesced mmio. There is little difference between +coalesced mmio and pio except that coalesced pio is used for ioport. + 5. The kvm_run structure ------------------------ -- 1.8.3.1
