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virtio: introduce VirtIOConfigSizeParams & virtio_get_config_size

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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.

All of the users of virtio_feature_get_config_size have been converted
to use virtio_get_config_size so it's no longer needed and is removed
with this commit.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Message-Id: <20220906073111.353245-2-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Daniil Tatianin 2022-09-06 10:31:07 +03:00 • committed by Michael S. Tsirkin
parent 8fcfc8235e
commit d74c30c811
4 changed files with 28 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

10
hw/virtio/virtio.c
View file

@ -3006,11 +3006,12 @@ int virtio_set_features(VirtIODevice *vdev, uint64_t val)
return ret;
}
size_t virtio_feature_get_config_size(const VirtIOFeature *feature_sizes,
uint64_t host_features)
size_t virtio_get_config_size(const VirtIOConfigSizeParams *params,
uint64_t host_features)
{
size_t config_size = 0;
int i;
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) {
@ -3018,6 +3019,7 @@ size_t virtio_feature_get_config_size(const VirtIOFeature *feature_sizes,
}
}
assert(config_size <= params->max_size);
return config_size;
}