On 2020/11/26 下午10:49, Stefano Garzarella wrote:
The get_config callback can be used by the device to fill the
config structure.
The callback will be invoked in vdpasim_get_config() before copying
bytes into caller buffer.

Move vDPA-net config updates from vdpasim_set_features() in the
new vdpasim_net_get_config() callback.

Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
---
  drivers/vdpa/vdpa_sim/vdpa_sim.c | 33 +++++++++++++++++++-------------
  1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index c07ddf6af720..8b87ce0485b6 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -58,6 +58,8 @@ struct vdpasim_virtqueue {
  #define VDPASIM_NET_FEATURES  (VDPASIM_FEATURES | \
                                 (1ULL << VIRTIO_NET_F_MAC))
+struct vdpasim;
+
  struct vdpasim_dev_attr {
        u64 supported_features;
        size_t config_size;
@@ -65,6 +67,7 @@ struct vdpasim_dev_attr {
        u32 id;
work_func_t work_fn;
+       void (*get_config)(struct vdpasim *vdpasim, void *config);
  };
/* State of each vdpasim device */
@@ -520,8 +523,6 @@ static u64 vdpasim_get_features(struct vdpa_device *vdpa)
  static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features)
  {
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
-       struct virtio_net_config *config =
-               (struct virtio_net_config *)vdpasim->config;
/* DMA mapping must be done by driver */
        if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
@@ -529,15 +530,6 @@ static int vdpasim_set_features(struct vdpa_device *vdpa, 
u64 features)
vdpasim->features = features & vdpasim->dev_attr.supported_features; - /* We generally only know whether guest is using the legacy interface
-        * here, so generally that's the earliest we can set config fields.
-        * Note: We actually require VIRTIO_F_ACCESS_PLATFORM above which
-        * implies VIRTIO_F_VERSION_1, but let's not try to be clever here.
-        */
-
-       config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
-       config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
-       memcpy(config->mac, macaddr_buf, ETH_ALEN);
return 0;
  }
@@ -593,8 +585,12 @@ static void vdpasim_get_config(struct vdpa_device *vdpa, 
unsigned int offset,
  {
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
- if (offset + len < vdpasim->dev_attr.config_size)
-               memcpy(buf, vdpasim->config + offset, len);
+       if (offset + len > vdpasim->dev_attr.config_size)
+               return;
+
+       vdpasim->dev_attr.get_config(vdpasim, vdpasim->config);
+
+       memcpy(buf, vdpasim->config + offset, len);
  }


I wonder how much value we can get from vdpasim->config consider we've already had get_config() method.

Is it possible to copy to the buffer directly here?

Thanks


static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
@@ -737,6 +733,16 @@ static const struct vdpa_config_ops 
vdpasim_batch_config_ops = {
        .free                   = vdpasim_free,
  };
+static void vdpasim_net_get_config(struct vdpasim *vdpasim, void *config)
+{
+       struct virtio_net_config *net_config =
+               (struct virtio_net_config *)config;
+
+       net_config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
+       net_config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
+       memcpy(net_config->mac, macaddr_buf, ETH_ALEN);
+}
+
  static int __init vdpasim_dev_init(void)
  {
        struct vdpasim_dev_attr dev_attr = {};
@@ -745,6 +751,7 @@ static int __init vdpasim_dev_init(void)
        dev_attr.supported_features = VDPASIM_NET_FEATURES;
        dev_attr.nvqs = VDPASIM_VQ_NUM;
        dev_attr.config_size = sizeof(struct virtio_net_config);
+       dev_attr.get_config = vdpasim_net_get_config;
        dev_attr.work_fn = vdpasim_net_work;
vdpasim_dev = vdpasim_create(&dev_attr);

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