[PATCH] KVM: Introduce generic interrupt injection for in-kernel irqchips

[Jan Kiszka <jan.kiszka@siemens.com>]

Currently, MSI messages can only be injected to in-kernel irqchips by
defining a corresponding IRQ route for each message. This is not only
unhandy if the MSI messages are generated "on the fly" by user space,
IRQ routes are a limited resource that user space has to manage
carefully.

By providing a direct injection path, we can both avoid using up limited
resources and simplify the necessary steps for user land. This path is
provide in a way that allows for use with other interrupt sources as
well. Besides MSIs also external interrupt lines can be manipulated
through this interface, obsoleting KVM_IRQ_LINE_STATUS.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

This picks up Avi's first suggestion as I still think it is the better
option to provide a direct MSI injection channel.

 Documentation/virtual/kvm/api.txt |   46 +++++++++++++++++++++++++++++++++++++
 include/linux/kvm.h               |   26 +++++++++++++++++++++
 include/linux/kvm_host.h          |    2 +
 virt/kvm/irq_comm.c               |   29 +++++++++++++++++++++++
 virt/kvm/kvm_main.c               |   20 ++++++++++++++++
 5 files changed, 123 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 81ff39f..c70be58 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1482,6 +1482,52 @@ See KVM_ASSIGN_DEV_IRQ for the data structure.  The target device is specified
 by assigned_dev_id.  In the flags field, only KVM_DEV_ASSIGN_MASK_INTX is
 evaluated.
 
+4.61 KVM_GENERAL_IRQ
+
+Capability: KVM_CAP_GENERAL_IRQ
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_general_irq (in/out)
+Returns: 0 on success, <0 on error
+
+Inject an interrupt event to the guest. Only valid if in-kernel irqchip is
+enabled.
+
+struct kvm_general_irq {
+	__u32 type;
+	__u32 op;
+	__s32 status;
+	__u32 pad;
+	union {
+		__u32 line;
+		struct {
+			__u32 address_lo;
+			__u32 address_hi;
+			__u32 data;
+		} msi;
+		__u8 pad[32];
+	} u;
+};
+
+Support IRQ types are:
+
+#define KVM_IRQTYPE_EXTERNAL_LINE	0
+#define KVM_IRQTYPE_MSI			1
+
+Available operations are:
+
+#define KVM_IRQOP_LOWER			0
+#define KVM_IRQOP_RAISE			1
+#define KVM_IRQOP_TRIGGER		2
+
+The level of an external interrupt line can either be raised or lowered, a
+MSI can only be triggered.
+
+If 0 is returned from the IOCTL, the status field was updated as well to
+reflect the injection result. It will be >0 on interrupt delivery, 0 if the
+interrupt was coalesced with an already pending one, and <0 if the guest
+blocked the delivery or some delivery error occurred.
+
 4.62 KVM_CREATE_SPAPR_TCE
 
 Capability: KVM_CAP_SPAPR_TCE
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 7a9dd4b..cb3afaf 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -590,6 +590,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_SYNC_REGS 74
 #define KVM_CAP_PCI_2_3 75
 #define KVM_CAP_KVMCLOCK_CTRL 76
+#define KVM_CAP_GENERAL_IRQ 77
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -715,6 +716,29 @@ struct kvm_one_reg {
 	__u64 addr;
 };
 
+#define KVM_IRQTYPE_EXTERNAL_LINE	0
+#define KVM_IRQTYPE_MSI			1
+
+#define KVM_IRQOP_LOWER			0
+#define KVM_IRQOP_RAISE			1
+#define KVM_IRQOP_TRIGGER		2
+
+struct kvm_general_irq {
+	__u32 type;
+	__u32 op;
+	__s32 status;
+	__u32 pad;
+	union {
+		__u32 line;
+		struct {
+			__u32 address_lo;
+			__u32 address_hi;
+			__u32 data;
+		} msi;
+		__u8 pad[32];
+	} u;
+};
+
 /*
  * ioctls for VM fds
  */
@@ -789,6 +813,8 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_PCI_2_3 */
 #define KVM_ASSIGN_SET_INTX_MASK  _IOW(KVMIO,  0xa4, \
 				       struct kvm_assigned_pci_dev)
+/* Available with KVM_CAP_GENERAL_IRQ */
+#define KVM_GENERAL_IRQ           _IOWR(KVMIO,  0xa5, struct kvm_general_irq)
 
 /*
  * ioctls for vcpu fds
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 49c2f2f..31d3b44 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -773,6 +773,8 @@ int kvm_set_irq_routing(struct kvm *kvm,
 			unsigned flags);
 void kvm_free_irq_routing(struct kvm *kvm);
 
+int kvm_general_irq(struct kvm *kvm, struct kvm_general_irq *irq);
+
 #else
 
 static inline void kvm_free_irq_routing(struct kvm *kvm) {}
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 9f614b4..e487d3f 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -138,6 +138,35 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
 	return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
 }
 
+int kvm_general_irq(struct kvm *kvm, struct kvm_general_irq *irq)
+{
+	struct kvm_kernel_irq_routing_entry route;
+
+	if (!irqchip_in_kernel(kvm))
+		return -EINVAL;
+
+	switch (irq->type) {
+	case KVM_IRQTYPE_EXTERNAL_LINE:
+		if (irq->op > KVM_IRQOP_RAISE)
+			return -EINVAL;
+		irq->status = kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID,
+					  irq->u.line, irq->op);
+		break;
+	case KVM_IRQTYPE_MSI:
+		if (irq->op != KVM_IRQOP_TRIGGER)
+			return -EINVAL;
+		route.msi.address_lo = irq->u.msi.address_lo;
+		route.msi.address_hi = irq->u.msi.address_hi;
+		route.msi.data = irq->u.msi.data;
+		irq->status = kvm_set_msi(&route, kvm,
+					  KVM_USERSPACE_IRQ_SOURCE_ID, 1);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
 /*
  * Return value:
  *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6bd34a6..95dffec 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2059,6 +2059,23 @@ static long kvm_vm_ioctl(struct file *filp,
 		mutex_unlock(&kvm->lock);
 		break;
 #endif
+#ifdef CONFIG_HAVE_KVM_IRQCHIP
+	case KVM_GENERAL_IRQ: {
+		struct kvm_general_irq irq;
+
+		r = -EFAULT;
+		if (copy_from_user(&irq, argp, sizeof(irq)))
+			goto out;
+		r = kvm_general_irq(kvm, &irq);
+		if (r < 0)
+			goto out;
+		if (copy_to_user(argp +
+				 offsetof(struct kvm_general_irq, status),
+				 &irq.status, sizeof(irq.status)))
+			r = -EFAULT;
+		break;
+	}
+#endif
 	default:
 		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
 		if (r == -ENOTTY)
@@ -2187,6 +2204,9 @@ static long kvm_dev_ioctl_check_extension_generic(long arg)
 	case KVM_CAP_SET_BOOT_CPU_ID:
 #endif
 	case KVM_CAP_INTERNAL_ERROR_DATA:
+#ifdef CONFIG_HAVE_KVM_IRQCHIP
+	case KVM_CAP_GENERAL_IRQ:
+#endif
 		return 1;
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 	case KVM_CAP_IRQ_ROUTING:
-- 
1.7.3.4