This is the first step towards moving all device config size calculation
logic into the virtio core code. In particular, this adds a struct that
contains all the necessary information for common virtio code to be able
to calculate the final config size for a device. This is expected to be
used with the new virtio_get_config_size helper, which calculates the
final length based on the provided host features.
This builds on top of already existing code like VirtIOFeature and
virtio_feature_get_config_size(), but adds additional fields, as well as
sanity checking so that device-specifc code doesn't have to duplicate it.
An example usage would be:
static const VirtIOFeature dev_features[] = {
{.flags = 1ULL << FEATURE_1_BIT,
.end = endof(struct virtio_dev_config, feature_1)},
{.flags = 1ULL << FEATURE_2_BIT,
.end = endof(struct virtio_dev_config, feature_2)},
{}
};
static const VirtIOConfigSizeParams dev_cfg_size_params = {
.min_size = DEV_BASE_CONFIG_SIZE,
.max_size = sizeof(struct virtio_dev_config),
.feature_sizes = dev_features
};
// code inside my_dev_device_realize()
size_t config_size = virtio_get_config_size(&dev_cfg_size_params,
host_features);
virtio_init(vdev, VIRTIO_ID_MYDEV, config_size);
Currently every device is expected to write its own boilerplate from the
example above in device_realize(), however, the next step of this
transition is moving VirtIOConfigSizeParams into VirtioDeviceClass,
so that it can be done automatically by the virtio initialization code.
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
---
hw/virtio/virtio.c | 17 +++++++++++++++++
include/hw/virtio/virtio.h | 9 +++++++++
2 files changed, 26 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 5d607aeaa0..8518382025 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3014,6 +3014,23 @@ size_t virtio_feature_get_config_size(const
VirtIOFeature *feature_sizes,
return config_size;
}
+size_t virtio_get_config_size(const VirtIOConfigSizeParams *params,
+ uint64_t host_features)
+{
+ size_t config_size = params->min_size;
+ const VirtIOFeature *feature_sizes = params->feature_sizes;
+ size_t i;
+
+ for (i = 0; feature_sizes[i].flags != 0; i++) {
+ if (host_features & feature_sizes[i].flags) {
+ config_size = MAX(feature_sizes[i].end, config_size);
+ }
+ }
+
+ assert(config_size <= params->max_size);
+ return config_size;
+}
+
int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
{
int i, ret;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index db1c0ddf6b..1991c58d9b 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -44,6 +44,15 @@ typedef struct VirtIOFeature {
size_t end;
} VirtIOFeature;
+typedef struct VirtIOConfigSizeParams {
+ size_t min_size;
+ size_t max_size;
+ const VirtIOFeature *feature_sizes;
+} VirtIOConfigSizeParams;
+
+size_t virtio_get_config_size(const VirtIOConfigSizeParams *params,
+ uint64_t host_features);
+
size_t virtio_feature_get_config_size(const VirtIOFeature *features,
uint64_t host_features);
--
2.25.1