Commit e9ea5069 authored by Jason Wang's avatar Jason Wang Committed by Paolo Bonzini
Browse files

kvm: add capability for any-length ioeventfds 



Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 931c33b1

Documentation/virtual/kvm/api.txt

+5 −1
Original line number Diff line number Diff line
@@ -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

include/uapi/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -830,6 +830,7 @@ struct kvm_ppc_smmu_info { 
#define KVM_CAP_GUEST_DEBUG_HW_BPS 119

#define KVM_CAP_GUEST_DEBUG_HW_WPS 120

#define KVM_CAP_SPLIT_IRQCHIP 121

#define KVM_CAP_IOEVENTFD_ANY_LENGTH 122



#ifdef KVM_CAP_IRQ_ROUTING

virt/kvm/eventfd.c

+1 −3
Original line number Diff line number Diff line
@@ -914,9 +914,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) 
		return -EINVAL;



	/* ioeventfd with no length can't be combined with DATAMATCH */

	if (!args->len &&

	    args->flags & (KVM_IOEVENTFD_FLAG_PIO |

			   KVM_IOEVENTFD_FLAG_DATAMATCH))

	if (!args->len && (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH))

		return -EINVAL;



	ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);

virt/kvm/kvm_main.c

+1 −0
Original line number Diff line number Diff line
@@ -2718,6 +2718,7 @@ 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_IOEVENTFD_ANY_LENGTH:

	case KVM_CAP_CHECK_EXTENSION_VM:

		return 1;

#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING