[PATCH v4 12/18] vdpa_sim: add get_config callback in vdpasim_dev_attr

From: Stefano Garzarella
Date: Tue Dec 15 2020 - 09:59:15 EST


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.
This is safe since in vdpa_get_config() we already check that
.set_features() callback is called before .get_config().

Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---
v4:
- explained in the commit message that the moving is safe [Jason]

v3:
- checked if get_config callback is set before call it
---
drivers/vdpa/vdpa_sim/vdpa_sim.c | 35 +++++++++++++++++++-------------
1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 4a0a6cadb9ff..5eadcd19ab6f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -68,6 +68,8 @@ 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;
@@ -75,6 +77,7 @@ struct vdpasim_dev_attr {
u32 id;

work_func_t work_fn;
+ void (*get_config)(struct vdpasim *vdpasim, void *config);
};

/* State of each vdpasim device */
@@ -530,8 +533,6 @@ 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)))
@@ -539,16 +540,6 @@ 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;
}

@@ -603,8 +594,13 @@ 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;
+
+ if (vdpasim->dev_attr.get_config)
+ vdpasim->dev_attr.get_config(vdpasim, vdpasim->config);
+
+ memcpy(buf, vdpasim->config + offset, len);
}

static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
@@ -747,6 +743,16 @@ 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 = {};
@@ -755,6 +761,7 @@ 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);
--
2.26.2