[RFC PATCH 07/27] vhost: Route guest->host notification through qemu

["Eugenio Pérez" <eperezma@redhat.com>]

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-sw-lm-ring.h |  26 +++++++++
 include/hw/virtio/vhost.h    |   3 ++
 hw/virtio/vhost-sw-lm-ring.c |  60 +++++++++++++++++++++
 hw/virtio/vhost.c            | 100 +++++++++++++++++++++++++++++++++--
 hw/virtio/meson.build        |   2 +-
 5 files changed, 187 insertions(+), 4 deletions(-)
 create mode 100644 hw/virtio/vhost-sw-lm-ring.h
 create mode 100644 hw/virtio/vhost-sw-lm-ring.c

diff --git a/hw/virtio/vhost-sw-lm-ring.h b/hw/virtio/vhost-sw-lm-ring.h
new file mode 100644
index 0000000000..86dc081b93
--- /dev/null
+++ b/hw/virtio/vhost-sw-lm-ring.h
@@ -0,0 +1,26 @@
+/*
+ * vhost software live migration ring
+ *
+ * SPDX-FileCopyrightText: Red Hat, Inc. 2020
+ * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef VHOST_SW_LM_RING_H
+#define VHOST_SW_LM_RING_H
+
+#include "qemu/osdep.h"
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/vhost.h"
+
+typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
+
+bool vhost_vring_kick(VhostShadowVirtqueue *vq);
+
+VhostShadowVirtqueue *vhost_sw_lm_shadow_vq(struct vhost_dev *dev, int idx);
+
+void vhost_sw_lm_shadow_vq_free(VhostShadowVirtqueue *vq);
+
+#endif
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index b5b7496537..93cc3f1ae3 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -54,6 +54,8 @@ struct vhost_iommu {
     QLIST_ENTRY(vhost_iommu) iommu_next;
 };
 
+typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
+
 typedef struct VhostDevConfigOps {
     /* Vhost device config space changed callback
      */
@@ -83,6 +85,7 @@ struct vhost_dev {
     bool started;
     bool log_enabled;
     uint64_t log_size;
+    VhostShadowVirtqueue *sw_lm_shadow_vq[2];
     VirtIOHandleOutput sw_lm_vq_handler;
     Error *migration_blocker;
     const VhostOps *vhost_ops;
diff --git a/hw/virtio/vhost-sw-lm-ring.c b/hw/virtio/vhost-sw-lm-ring.c
new file mode 100644
index 0000000000..0192e77831
--- /dev/null
+++ b/hw/virtio/vhost-sw-lm-ring.c
@@ -0,0 +1,60 @@
+/*
+ * vhost software live migration ring
+ *
+ * SPDX-FileCopyrightText: Red Hat, Inc. 2020
+ * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "hw/virtio/vhost-sw-lm-ring.h"
+#include "hw/virtio/vhost.h"
+
+#include "standard-headers/linux/vhost_types.h"
+#include "standard-headers/linux/virtio_ring.h"
+
+#include "qemu/event_notifier.h"
+
+typedef struct VhostShadowVirtqueue {
+    EventNotifier hdev_notifier;
+    VirtQueue *vq;
+} VhostShadowVirtqueue;
+
+static inline bool vhost_vring_should_kick(VhostShadowVirtqueue *vq)
+{
+    return virtio_queue_get_used_notify_split(vq->vq);
+}
+
+bool vhost_vring_kick(VhostShadowVirtqueue *vq)
+{
+    return vhost_vring_should_kick(vq) ? event_notifier_set(&vq->hdev_notifier)
+                                       : true;
+}
+
+VhostShadowVirtqueue *vhost_sw_lm_shadow_vq(struct vhost_dev *dev, int idx)
+{
+    struct vhost_vring_file file = {
+        .index = idx
+    };
+    VirtQueue *vq = virtio_get_queue(dev->vdev, idx);
+    VhostShadowVirtqueue *svq;
+    int r;
+
+    svq = g_new0(VhostShadowVirtqueue, 1);
+    svq->vq = vq;
+
+    r = event_notifier_init(&svq->hdev_notifier, 0);
+    assert(r == 0);
+
+    file.fd = event_notifier_get_fd(&svq->hdev_notifier);
+    r = dev->vhost_ops->vhost_set_vring_kick(dev, &file);
+    assert(r == 0);
+
+    return svq;
+}
+
+void vhost_sw_lm_shadow_vq_free(VhostShadowVirtqueue *vq)
+{
+    event_notifier_cleanup(&vq->hdev_notifier);
+    g_free(vq);
+}
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 9cbd52a7f1..a55b684b5f 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -13,6 +13,8 @@
  * GNU GPL, version 2 or (at your option) any later version.
  */
 
+#include "hw/virtio/vhost-sw-lm-ring.h"
+
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "hw/virtio/vhost.h"
@@ -61,6 +63,20 @@ bool vhost_has_free_slot(void)
     return slots_limit > used_memslots;
 }
 
+static struct vhost_dev *vhost_dev_from_virtio(const VirtIODevice *vdev)
+{
+    struct vhost_dev *hdev;
+
+    QLIST_FOREACH(hdev, &vhost_devices, entry) {
+        if (hdev->vdev == vdev) {
+            return hdev;
+        }
+    }
+
+    assert(hdev);
+    return NULL;
+}
+
 static bool vhost_dev_can_log(const struct vhost_dev *hdev)
 {
     return hdev->features & (0x1ULL << VHOST_F_LOG_ALL);
@@ -148,6 +164,12 @@ static int vhost_sync_dirty_bitmap(struct vhost_dev *dev,
     return 0;
 }
 
+static void vhost_log_sync_nop(MemoryListener *listener,
+                               MemoryRegionSection *section)
+{
+    return;
+}
+
 static void vhost_log_sync(MemoryListener *listener,
                           MemoryRegionSection *section)
 {
@@ -928,6 +950,71 @@ static void vhost_log_global_stop(MemoryListener *listener)
     }
 }
 
+static void handle_sw_lm_vq(VirtIODevice *vdev, VirtQueue *vq)
+{
+    struct vhost_dev *hdev = vhost_dev_from_virtio(vdev);
+    uint16_t idx = virtio_get_queue_index(vq);
+
+    VhostShadowVirtqueue *svq = hdev->sw_lm_shadow_vq[idx];
+
+    vhost_vring_kick(svq);
+}
+
+static int vhost_sw_live_migration_stop(struct vhost_dev *dev)
+{
+    int idx;
+
+    vhost_dev_enable_notifiers(dev, dev->vdev);
+    for (idx = 0; idx < dev->nvqs; ++idx) {
+        vhost_sw_lm_shadow_vq_free(dev->sw_lm_shadow_vq[idx]);
+    }
+
+    return 0;
+}
+
+static int vhost_sw_live_migration_start(struct vhost_dev *dev)
+{
+    int idx;
+
+    for (idx = 0; idx < dev->nvqs; ++idx) {
+        dev->sw_lm_shadow_vq[idx] = vhost_sw_lm_shadow_vq(dev, idx);
+    }
+
+    vhost_dev_disable_notifiers(dev, dev->vdev);
+
+    return 0;
+}
+
+static int vhost_sw_live_migration_enable(struct vhost_dev *dev,
+                                          bool enable_lm)
+{
+    if (enable_lm) {
+        return vhost_sw_live_migration_start(dev);
+    } else {
+        return vhost_sw_live_migration_stop(dev);
+    }
+}
+
+static void vhost_sw_lm_global_start(MemoryListener *listener)
+{
+    int r;
+
+    r = vhost_migration_log(listener, true, vhost_sw_live_migration_enable);
+    if (r < 0) {
+        abort();
+    }
+}
+
+static void vhost_sw_lm_global_stop(MemoryListener *listener)
+{
+    int r;
+
+    r = vhost_migration_log(listener, false, vhost_sw_live_migration_enable);
+    if (r < 0) {
+        abort();
+    }
+}
+
 static void vhost_log_start(MemoryListener *listener,
                             MemoryRegionSection *section,
                             int old, int new)
@@ -1334,9 +1421,14 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         .region_nop = vhost_region_addnop,
         .log_start = vhost_log_start,
         .log_stop = vhost_log_stop,
-        .log_sync = vhost_log_sync,
-        .log_global_start = vhost_log_global_start,
-        .log_global_stop = vhost_log_global_stop,
+        .log_sync = !vhost_dev_can_log(hdev) ?
+                    vhost_log_sync_nop :
+                    vhost_log_sync,
+        .log_global_start = !vhost_dev_can_log(hdev) ?
+                            vhost_sw_lm_global_start :
+                            vhost_log_global_start,
+        .log_global_stop = !vhost_dev_can_log(hdev) ? vhost_sw_lm_global_stop :
+                                                      vhost_log_global_stop,
         .eventfd_add = vhost_eventfd_add,
         .eventfd_del = vhost_eventfd_del,
         .priority = 10
@@ -1364,6 +1456,8 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
             error_free(hdev->migration_blocker);
             goto fail_busyloop;
         }
+    } else {
+        hdev->sw_lm_vq_handler = handle_sw_lm_vq;
     }
 
     hdev->mem = g_malloc0(offsetof(struct vhost_memory, regions));
diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
index fbff9bc9d4..17419cb13e 100644
--- a/hw/virtio/meson.build
+++ b/hw/virtio/meson.build
@@ -11,7 +11,7 @@ softmmu_ss.add(when: 'CONFIG_ALL', if_true: files('vhost-stub.c'))
 
 virtio_ss = ss.source_set()
 virtio_ss.add(files('virtio.c'))
-virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 'vhost-backend.c'))
+virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 'vhost-backend.c', 'vhost-sw-lm-ring.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_USER', if_true: files('vhost-user.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_VDPA', if_true: files('vhost-vdpa.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true: files('virtio-balloon.c'))
-- 
2.18.4