Re: [Qemu-devel] [[RFC v3 03/12] virtio: init memory cache for packed ring

[Wei Xu]

On Mon, Oct 15, 2018 at 11:10:12AM +0800, Jason Wang wrote:
> 
> 
> On 2018年10月11日 22:08, address@hidden wrote:
> >From: Wei Xu <address@hidden>
> >
> >Expand 1.0 by adding offset calculation accordingly.
> 
> This is only part of what this patch did and I suggest to another patch to
> do this.
> 
> >
> >Signed-off-by: Wei Xu <address@hidden>
> >---
> >  hw/virtio/vhost.c          | 16 ++++++++--------
> >  hw/virtio/virtio.c         | 35 +++++++++++++++++++++++------------
> >  include/hw/virtio/virtio.h |  4 ++--
> >  3 files changed, 33 insertions(+), 22 deletions(-)
> >
> >diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> >index 569c405..9df2da3 100644
> >--- a/hw/virtio/vhost.c
> >+++ b/hw/virtio/vhost.c
> >@@ -996,14 +996,14 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
> >          r = -ENOMEM;
> >          goto fail_alloc_desc;
> >      }
> >-    vq->avail_size = s = l = virtio_queue_get_avail_size(vdev, idx);
> >+    vq->avail_size = s = l = virtio_queue_get_driver_size(vdev, idx);
> 
> Let's try to use a more consistent name. E.g either use avail/used or
> driver/device.
> 
> I prefer to use avail/used, it can save lots of unnecessary changes.

OK.

> 
> >      vq->avail_phys = a = virtio_queue_get_avail_addr(vdev, idx);
> >      vq->avail = vhost_memory_map(dev, a, &l, 0);
> >      if (!vq->avail || l != s) {
> >          r = -ENOMEM;
> >          goto fail_alloc_avail;
> >      }
> >-    vq->used_size = s = l = virtio_queue_get_used_size(vdev, idx);
> >+    vq->used_size = s = l = virtio_queue_get_device_size(vdev, idx);
> >      vq->used_phys = a = virtio_queue_get_used_addr(vdev, idx);
> >      vq->used = vhost_memory_map(dev, a, &l, 1);
> >      if (!vq->used || l != s) {
> >@@ -1051,10 +1051,10 @@ static int vhost_virtqueue_start(struct vhost_dev 
> >*dev,
> >  fail_vector:
> >  fail_kick:
> >  fail_alloc:
> >-    vhost_memory_unmap(dev, vq->used, virtio_queue_get_used_size(vdev, idx),
> >+    vhost_memory_unmap(dev, vq->used, virtio_queue_get_device_size(vdev, 
> >idx),
> >                         0, 0);
> >  fail_alloc_used:
> >-    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_avail_size(vdev, 
> >idx),
> >+    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_driver_size(vdev, 
> >idx),
> >                         0, 0);
> >  fail_alloc_avail:
> >      vhost_memory_unmap(dev, vq->desc, virtio_queue_get_desc_size(vdev, 
> > idx),
> >@@ -1101,10 +1101,10 @@ static void vhost_virtqueue_stop(struct vhost_dev 
> >*dev,
> >                                                  vhost_vq_index);
> >      }
> >-    vhost_memory_unmap(dev, vq->used, virtio_queue_get_used_size(vdev, idx),
> >-                       1, virtio_queue_get_used_size(vdev, idx));
> >-    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_avail_size(vdev, 
> >idx),
> >-                       0, virtio_queue_get_avail_size(vdev, idx));
> >+    vhost_memory_unmap(dev, vq->used, virtio_queue_get_device_size(vdev, 
> >idx),
> >+                       1, virtio_queue_get_device_size(vdev, idx));
> >+    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_driver_size(vdev, 
> >idx),
> >+                       0, virtio_queue_get_driver_size(vdev, idx));
> >      vhost_memory_unmap(dev, vq->desc, virtio_queue_get_desc_size(vdev, 
> > idx),
> >                         0, virtio_queue_get_desc_size(vdev, idx));
> >  }
> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >index 500eecf..bfb3364 100644
> >--- a/hw/virtio/virtio.c
> >+++ b/hw/virtio/virtio.c
> >@@ -162,11 +162,8 @@ static void virtio_init_region_cache(VirtIODevice 
> >*vdev, int n)
> >      VRingMemoryRegionCaches *old = vq->vring.caches;
> >      VRingMemoryRegionCaches *new = NULL;
> >      hwaddr addr, size;
> >-    int event_size;
> >      int64_t len;
> >-    event_size = virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX) 
> >? 2 : 0;
> >-
> >      addr = vq->vring.desc;
> >      if (!addr) {
> >          goto out_no_cache;
> >@@ -174,13 +171,13 @@ static void virtio_init_region_cache(VirtIODevice 
> >*vdev, int n)
> >      new = g_new0(VRingMemoryRegionCaches, 1);
> >      size = virtio_queue_get_desc_size(vdev, n);
> >      len = address_space_cache_init(&new->desc, vdev->dma_as,
> >-                                   addr, size, false);
> >+                                   addr, size, true);
> 
> This looks wrong, for split virtqueue, descriptor ring is read only.

Did know it, I got a segment fault with 'false' case for packed ring,
will add a feature check here, thanks for the tip.

> 
> >      if (len < size) {
> >          virtio_error(vdev, "Cannot map desc");
> >          goto err_desc;
> >      }
> >-    size = virtio_queue_get_used_size(vdev, n) + event_size;
> >+    size = virtio_queue_get_device_size(vdev, n);
> >      len = address_space_cache_init(&new->used, vdev->dma_as,
> >                                     vq->vring.used, size, true);
> >      if (len < size) {
> >@@ -188,7 +185,7 @@ static void virtio_init_region_cache(VirtIODevice *vdev, 
> >int n)
> >          goto err_used;
> >      }
> >-    size = virtio_queue_get_avail_size(vdev, n) + event_size;
> >+    size = virtio_queue_get_driver_size(vdev, n);
> >      len = address_space_cache_init(&new->avail, vdev->dma_as,
> >                                     vq->vring.avail, size, false);
> >      if (len < size) {
> >@@ -2339,16 +2336,30 @@ hwaddr virtio_queue_get_desc_size(VirtIODevice 
> >*vdev, int n)
> >      return sizeof(VRingDesc) * vdev->vq[n].vring.num;
> >  }
> >-hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n)
> >+hwaddr virtio_queue_get_driver_size(VirtIODevice *vdev, int n)
> >  {
> >-    return offsetof(VRingAvail, ring) +
> >-        sizeof(uint16_t) * vdev->vq[n].vring.num;
> >+    int s;
> >+
> >+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+        return sizeof(struct VRingPackedDescEvent);
> >+    } else {
> >+        s = virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> >+        return offsetof(VRingAvail, ring) +
> >+            sizeof(uint16_t) * vdev->vq[n].vring.num + s;
> 
> I tend to move this to an independent patch.

You mean this two functions?

Wei

> 
> Thanks
> 
> >+    }
> >  }
> >-hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
> >+hwaddr virtio_queue_get_device_size(VirtIODevice *vdev, int n)
> >  {
> >-    return offsetof(VRingUsed, ring) +
> >-        sizeof(VRingUsedElem) * vdev->vq[n].vring.num;
> >+    int s;
> >+
> >+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+        return sizeof(struct VRingPackedDescEvent);
> >+    } else {
> >+        s = virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> >+        return offsetof(VRingUsed, ring) +
> >+            sizeof(VRingUsedElem) * vdev->vq[n].vring.num + s;
> >+    }
> >  }
> >  uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> >diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >index 9c1fa07..e323e76 100644
> >--- a/include/hw/virtio/virtio.h
> >+++ b/include/hw/virtio/virtio.h
> >@@ -270,8 +270,8 @@ hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, 
> >int n);
> >  hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n);
> >  hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
> >  hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
> >-hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
> >-hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
> >+hwaddr virtio_queue_get_driver_size(VirtIODevice *vdev, int n);
> >+hwaddr virtio_queue_get_device_size(VirtIODevice *vdev, int n);
> >  uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> >  void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t 
> > idx);
> >  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);
> 
>