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authorJason Wang <jasowang@redhat.com>2015-09-15 14:41:59 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2015-10-01 15:06:31 +0200
commite9ea5069d9e569c32ab913c39467df32e056b3a7 (patch)
tree1e3e34946e2875564aa7a85a454f851d1575dac8 /Documentation/virtual
parent931c33b178b091cced2a6b3f57f04655f8ff5207 (diff)
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kvm: add capability for any-length ioeventfds
Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt6
1 files changed, 5 insertions, 1 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e3e9c41721a2..34cc068e81ea 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