virtio: support setting memory region based host notifier

This patch introduces the support for setting memory region
based host notifiers for virtio device. This is helpful when
using a hardware accelerator for a virtio device, because
hardware heavily depends on the notification, this will allow
the guest driver in the VM to notify the hardware directly.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 1e8ab7bbc5..5eb0c323ca 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1037,6 +1037,27 @@ assign_error:
     return r;
 }
 
+static int virtio_pci_set_host_notifier_mr(DeviceState *d, int n,
+                                           MemoryRegion *mr, bool assign)
+{
+    VirtIOPCIProxy *proxy = to_virtio_pci_proxy(d);
+    int offset;
+
+    if (n >= VIRTIO_QUEUE_MAX || !virtio_pci_modern(proxy) ||
+        virtio_pci_queue_mem_mult(proxy) != memory_region_size(mr)) {
+        return -1;
+    }
+
+    if (assign) {
+        offset = virtio_pci_queue_mem_mult(proxy) * n;
+        memory_region_add_subregion_overlap(&proxy->notify.mr, offset, mr, 1);
+    } else {
+        memory_region_del_subregion(&proxy->notify.mr, mr);
+    }
+
+    return 0;
+}
+
 static void virtio_pci_vmstate_change(DeviceState *d, bool running)
 {
     VirtIOPCIProxy *proxy = to_virtio_pci_proxy(d);
@@ -2652,6 +2673,7 @@ static void virtio_pci_bus_class_init(ObjectClass *klass, void *data)
     k->has_extra_state = virtio_pci_has_extra_state;
     k->query_guest_notifiers = virtio_pci_query_guest_notifiers;
     k->set_guest_notifiers = virtio_pci_set_guest_notifiers;
+    k->set_host_notifier_mr = virtio_pci_set_host_notifier_mr;
     k->vmstate_change = virtio_pci_vmstate_change;
     k->pre_plugged = virtio_pci_pre_plugged;
     k->device_plugged = virtio_pci_device_plugged;