KVM: Introduce direct MSI message injection for in-kernel irqchips

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.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 31 insertions, 0 deletions

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index f63ccb0a5982..28694f4a9139 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -18,3 +18,6 @@ config KVM_MMIO
 
 config KVM_ASYNC_PF
        bool
+
+config HAVE_KVM_MSI
+       bool
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 9f614b4e365f..a6a0365475ed 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -138,6 +138,20 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
         return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
 }
 
+int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
+{
+        struct kvm_kernel_irq_routing_entry route;
+
+        if (!irqchip_in_kernel(kvm) || msi->flags != 0)
+                return -EINVAL;
+
+        route.msi.address_lo = msi->address_lo;
+        route.msi.address_hi = msi->address_hi;
+        route.msi.data = msi->data;
+
+        return kvm_set_msi(&route, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
+}
+
 /*
  * 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 9eb7936e491d..1847c762d8d9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2060,6 +2060,17 @@ static long kvm_vm_ioctl(struct file *filp,
                 mutex_unlock(&kvm->lock);
                 break;
 #endif
+#ifdef CONFIG_HAVE_KVM_MSI
+        case KVM_SIGNAL_MSI: {
+                struct kvm_msi msi;
+
+                r = -EFAULT;
+                if (copy_from_user(&msi, argp, sizeof msi))
+                        goto out;
+                r = kvm_send_userspace_msi(kvm, &msi);
+                break;
+        }
+#endif
         default:
                 r = kvm_arch_vm_ioctl(filp, ioctl, arg);
                 if (r == -ENOTTY)
@@ -2188,6 +2199,9 @@ 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_MSI
+        case KVM_CAP_SIGNAL_MSI:
+#endif
                 return 1;
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
         case KVM_CAP_IRQ_ROUTING: