From e9ea5069d9e569c32ab913c39467df32e056b3a7 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Tue, 15 Sep 2015 14:41:59 +0800 Subject: kvm: add capability for any-length ioeventfds Cc: Gleb Natapov Cc: Paolo Bonzini Signed-off-by: Jason Wang Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/api.txt | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'Documentation/virtual') diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index e3e9c41..34cc068 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -1604,7 +1604,7 @@ provided event instead of triggering an exit. struct kvm_ioeventfd { __u64 datamatch; __u64 addr; /* legal pio/mmio address */ - __u32 len; /* 1, 2, 4, or 8 bytes */ + __u32 len; /* 0, 1, 2, 4, or 8 bytes */ __s32 fd; __u32 flags; __u8 pad[36]; @@ -1627,6 +1627,10 @@ to the registered address is equal to datamatch in struct kvm_ioeventfd. For virtio-ccw devices, addr contains the subchannel id and datamatch the virtqueue index. +With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and +the kernel will ignore the length of guest write and may get a faster vmexit. +The speedup may only apply to specific architectures, but the ioeventfd will +work anyway. 4.60 KVM_DIRTY_TLB -- cgit v1.1