Cc: Gleb Natapov <g...@kernel.org>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
Documentation/virtual/kvm/api.txt | 7 ++++++-
include/uapi/linux/kvm.h | 1 +
virt/kvm/kvm_main.c | 1 +
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index d9eccee..26661ef 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1598,7 +1598,7 @@ 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];
@@ -1621,6 +1621,11 @@ 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_FAST_MMIO, a zero length mmio eventfd is allowed for
+kernel to ignore the length of guest write and get a possible faster
+response. Note the speedup may only work on some specific
+architectures and setups. Otherwise, it's as fast as wildcard mmio
+eventfd.
4.60 KVM_DIRTY_TLB
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a9256f0..ad72a61 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -824,6 +824,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_MULTI_ADDRESS_SPACE 118
#define KVM_CAP_GUEST_DEBUG_HW_BPS 119
#define KVM_CAP_GUEST_DEBUG_HW_WPS 120
+#define KVM_CAP_FAST_MMIO 121
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9af68db..645f55d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2717,6 +2717,7 @@ static long kvm_vm_ioctl_check_extension_generic(struct
kvm *kvm, long arg)
case KVM_CAP_IRQFD:
case KVM_CAP_IRQFD_RESAMPLE:
#endif
+ case KVM_CAP_FAST_MMIO:
case KVM_CAP_CHECK_EXTENSION_VM:
return 1;
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
--
2.1.4
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