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Groups > linux.kernel > #1234026

[FYI PATCH 12/20] kvm: add capability for any-length ioeventfds

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From: Jason Wang <jasowang@redhat.com>

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>
---
 Documentation/virtual/kvm/api.txt | 6 +++++-
 include/uapi/linux/kvm.h          | 1 +
 virt/kvm/eventfd.c                | 4 +---
 virt/kvm/kvm_main.c               | 1 +
 4 files changed, 8 insertions(+), 4 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
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 12e3afbf0f47..03f3618612aa 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -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
 
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 79db45336e3a..ac89299b8699 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -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);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 23116dcb2129..afd7ae6aec65 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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
-- 
1.8.3.1


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Thread

[FYI PATCH 00/20] kvm/queue will be merged soon to kvm/next Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:40 +0200
  [FYI PATCH 03/20] KVM: x86: replace vm_has_apicv hook with cpu_uses_apicv Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:40 +0200
  [FYI PATCH 15/20] kvm/x86: Hyper-V HV_X64_MSR_VP_RUNTIME support Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:40 +0200
  [FYI PATCH 12/20] kvm: add capability for any-length ioeventfds Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:40 +0200
  [FYI PATCH 20/20] KVM: vmx: disable posted interrupts if no local APIC Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 04/20] KVM: x86: introduce lapic_in_kernel Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 11/20] kvm: add tracepoint for fast mmio Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 17/20] KVM: VMX: introduce __vmx_flush_tlb to handle specific vpid Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 09/20] KVM: x86: Add support for local interrupt requests from userspace Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 10/20] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 19/20] KVM: nVMX: nested VPID emulation Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 18/20] KVM: nVMX: emulate the INVVPID instruction Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 06/20] KVM: x86: Split the APIC from the rest of IRQCHIP. Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 07/20] KVM: x86: Add KVM exit for IOAPIC EOIs Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 05/20] KVM: x86: unify handling of interrupt window Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 13/20] kvm/x86: Hyper-V HV_X64_MSR_RESET msr Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 14/20] kvm/x86: Hyper-V HV_X64_MSR_VP_INDEX export for QEMU. Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 02/20] KVM: x86: store IOAPIC-handled vectors in each VCPU Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200
  [FYI PATCH 01/20] KVM: x86: set TMR when the interrupt is accepted Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 12:50 +0200

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