Re: [RFC PATCH v4 12/20] virtio: Add vhost_shadow_vq_get_vring_addr

[Jason Wang]

在 2021/10/1 下午3:05, Eugenio Pérez 写道:
It reports the shadow virtqueue address from qemu virtual address space


I think both the title and commit log needs to more tweaks. Looking at 
the codes, what id does is actually introduce vring into svq.



Signed-off-by: Eugenio Pérez <epere...@redhat.com>
---
  hw/virtio/vhost-shadow-virtqueue.h |  4 +++
  hw/virtio/vhost-shadow-virtqueue.c | 50 ++++++++++++++++++++++++++++++
  2 files changed, 54 insertions(+)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
b/hw/virtio/vhost-shadow-virtqueue.h
index 237cfceb9c..2df3d117f5 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -16,6 +16,10 @@ typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
  
  EventNotifier *vhost_svq_get_svq_call_notifier(VhostShadowVirtqueue *svq);
  void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int 
call_fd);
+void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
+                              struct vhost_vring_addr *addr);
+size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq);
+size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq);
  
  bool vhost_svq_start(struct vhost_dev *dev, unsigned idx,
                       VhostShadowVirtqueue *svq);
diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index 3fe129cf63..5c1899f6af 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -18,6 +18,9 @@
  
  /* Shadow virtqueue to relay notifications */
  typedef struct VhostShadowVirtqueue {
+    /* Shadow vring */
+    struct vring vring;
+
      /* Shadow kick notifier, sent to vhost */
      EventNotifier kick_notifier;
      /* Shadow call notifier, sent to vhost */
@@ -38,6 +41,9 @@ typedef struct VhostShadowVirtqueue {
  
      /* Virtio queue shadowing */
      VirtQueue *vq;
+
+    /* Virtio device */
+    VirtIODevice *vdev;
  } VhostShadowVirtqueue;
  
  /* Forward guest notifications */
@@ -93,6 +99,35 @@ void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue 
*svq, int call_fd)
      event_notifier_init_fd(&svq->guest_call_notifier, call_fd);
  }
  
+/*
+ * Get the shadow vq vring address.
+ * @svq Shadow virtqueue
+ * @addr Destination to store address
+ */
+void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
+                              struct vhost_vring_addr *addr)
+{
+    addr->desc_user_addr = (uint64_t)svq->vring.desc;
+    addr->avail_user_addr = (uint64_t)svq->vring.avail;
+    addr->used_user_addr = (uint64_t)svq->vring.used;
+}
+
+size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq)
+{
+    uint16_t vq_idx = virtio_get_queue_index(svq->vq);
+    size_t desc_size = virtio_queue_get_desc_size(svq->vdev, vq_idx);
+    size_t avail_size = virtio_queue_get_avail_size(svq->vdev, vq_idx);
+
+    return ROUND_UP(desc_size + avail_size, qemu_real_host_page_size);


Is this round up required by the spec?


+}
+
+size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq)
+{
+    uint16_t vq_idx = virtio_get_queue_index(svq->vq);
+    size_t used_size = virtio_queue_get_used_size(svq->vdev, vq_idx);
+    return ROUND_UP(used_size, qemu_real_host_page_size);
+}
+
  /*
   * Restore the vhost guest to host notifier, i.e., disables svq effect.
   */
@@ -178,6 +213,10 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
  VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
  {
      int vq_idx = dev->vq_index + idx;
+    unsigned num = virtio_queue_get_num(dev->vdev, vq_idx);
+    size_t desc_size = virtio_queue_get_desc_size(dev->vdev, vq_idx);
+    size_t driver_size;
+    size_t device_size;
      g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
      int r;
  
@@ -196,6 +235,15 @@ VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
      }
  
      svq->vq = virtio_get_queue(dev->vdev, vq_idx);
+    svq->vdev = dev->vdev;
+    driver_size = vhost_svq_driver_area_size(svq);
+    device_size = vhost_svq_device_area_size(svq);
+    svq->vring.num = num;
+    svq->vring.desc = qemu_memalign(qemu_real_host_page_size, driver_size);
+    svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
+    memset(svq->vring.desc, 0, driver_size);


Any reason for using the contiguous area for both desc and avail?

Thanks


+    svq->vring.used = qemu_memalign(qemu_real_host_page_size, device_size);
+    memset(svq->vring.used, 0, device_size);
      event_notifier_set_handler(&svq->call_notifier,
                                 vhost_svq_handle_call);
      return g_steal_pointer(&svq);
@@ -215,5 +263,7 @@ void vhost_svq_free(VhostShadowVirtqueue *vq)
      event_notifier_cleanup(&vq->kick_notifier);
      event_notifier_set_handler(&vq->call_notifier, NULL);
      event_notifier_cleanup(&vq->call_notifier);
+    qemu_vfree(vq->vring.desc);
+    qemu_vfree(vq->vring.used);
      g_free(vq);
  }