[v2,08/17] KVM: x86/xen: Support direct injection of event channel events

Commit Message

David Woodhouse Feb. 28, 2022, 8:05 p.m. UTC

From: David Woodhouse <[e-mail]>

This adds a KVM_XEN_HVM_EVTCHN_SEND ioctl which allows direct injection
of events given an explicit { vcpu, port, priority } in precisely the
same form that those fields are given in the IRQ routing table.

Userspace is currently able to inject 2-level events purely by setting
the bits in the shared_info and vcpu_info, but FIFO event channels are
harder to deal with; we will need the kernel to take sole ownership of
delivery when we support those.

A patch advertising this feature with a new bit in the KVM_CAP_XEN_HVM
ioctl will be added in a subsequent patch.

Signed-off-by: David Woodhouse <[e-mail]>
---
 arch/x86/kvm/x86.c       |  9 +++++++++
 arch/x86/kvm/xen.c       | 32 ++++++++++++++++++++++++++++++++
 arch/x86/kvm/xen.h       |  1 +
 include/uapi/linux/kvm.h |  3 +++
 4 files changed, 45 insertions(+)

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fd16615cc0f2..a6ba50c9928b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6476,6 +6476,15 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_xen_hvm_set_attr(kvm, &xha);
 		break;
 	}
+	case KVM_XEN_HVM_EVTCHN_SEND: {
+		struct kvm_irq_routing_xen_evtchn uxe;
+
+		r = -EFAULT;
+		if (copy_from_user(&uxe, argp, sizeof(uxe)))
+			goto out;
+		r = kvm_xen_hvm_evtchn_send(kvm, &uxe);
+		break;
+	}
 #endif
 	case KVM_SET_CLOCK:
 		r = kvm_vm_ioctl_set_clock(kvm, argp);
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9c87263a5be2..f0f0011c4617 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1086,6 +1086,38 @@  int kvm_xen_setup_evtchn(struct kvm *kvm,
 	return 0;
 }
 
+/*
+ * Explicit event sending from userspace with KVM_XEN_HVM_EVTCHN_SEND ioctl.
+ */
+int kvm_xen_hvm_evtchn_send(struct kvm *kvm, struct kvm_irq_routing_xen_evtchn *uxe)
+{
+	struct kvm_xen_evtchn e;
+	int ret;
+
+	if (!uxe->port || uxe->port >= max_evtchn_port(kvm))
+		return -EINVAL;
+
+	/* We only support 2 level event channels for now */
+	if (uxe->priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
+		return -EINVAL;
+
+	e.port = uxe->port;
+	e.vcpu_id = uxe->vcpu;
+	e.vcpu_idx = -1;
+	e.priority = uxe->priority;
+
+	ret = kvm_xen_set_evtchn(&e, kvm);
+
+	/*
+	 * None of that 'return 1 if it actually got delivered' nonsense.
+	 * We don't care if it was masked (-ENOTCONN) either.
+	 */
+	if (ret > 0 || ret == -ENOTCONN)
+		ret = 0;
+
+	return ret;
+}
+
 void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
 {
 	kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index e28feb32add6..852286de574e 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -20,6 +20,7 @@  int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data);
 int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
+int kvm_xen_hvm_evtchn_send(struct kvm *kvm, struct kvm_irq_routing_xen_evtchn *evt);
 int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data);
 int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc);
 void kvm_xen_init_vm(struct kvm *kvm);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d2f1efc3aa35..415d8fe5c624 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1698,6 +1698,9 @@  struct kvm_xen_hvm_attr {
 #define KVM_XEN_VCPU_GET_ATTR	_IOWR(KVMIO, 0xca, struct kvm_xen_vcpu_attr)
 #define KVM_XEN_VCPU_SET_ATTR	_IOW(KVMIO,  0xcb, struct kvm_xen_vcpu_attr)
 
+/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_EVTCHN_SEND */
+#define KVM_XEN_HVM_EVTCHN_SEND	_IOW(KVMIO,  0xd0, struct kvm_irq_routing_xen_evtchn)
+
 #define KVM_GET_SREGS2             _IOR(KVMIO,  0xcc, struct kvm_sregs2)
 #define KVM_SET_SREGS2             _IOW(KVMIO,  0xcd, struct kvm_sregs2)