[libvirt PATCH v3 05/21] nodedev: add ability to list and parse defined mdevs

[Daniel P. Berrangé]

On Thu, Dec 24, 2020 at 08:14:29AM -0600, Jonathon Jongsma wrote:
> This adds some internal API to query for persistent mediated devices
> that are defined by mdevctl. Following commits will make use of this
> information. This just provides the infrastructure and tests for this
> feature. One test verifies that we are executing mdevctl with the proper
> arguments, and the other test verifies that we can parse the returned
> JSON and convert it to our own internal node device representations.
> 
> Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
> ---
>  src/node_device/node_device_driver.c          | 150 ++++++++++++++++++
>  src/node_device/node_device_driver.h          |   7 +
>  .../mdevctl-list-defined.argv                 |   1 +
>  .../mdevctl-list-multiple.json                |  59 +++++++
>  .../mdevctl-list-multiple.out.xml             |  39 +++++
>  tests/nodedevmdevctltest.c                    |  95 ++++++++++-
>  6 files changed, 349 insertions(+), 2 deletions(-)
>  create mode 100644 tests/nodedevmdevctldata/mdevctl-list-defined.argv
>  create mode 100644 tests/nodedevmdevctldata/mdevctl-list-multiple.json
>  create mode 100644 tests/nodedevmdevctldata/mdevctl-list-multiple.out.xml
> 
> diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c
> index 6143459618..bbd373e32e 100644
> --- a/src/node_device/node_device_driver.c
> +++ b/src/node_device/node_device_driver.c
> @@ -853,6 +853,156 @@ virMdevctlStop(virNodeDeviceDefPtr def)
>  }

> +int
> +nodeDeviceParseMdevctlJSON(const char *jsonstring,
> +                           virNodeDeviceDefPtr **devs)
> +{
> +    int n;
> +    g_autoptr(virJSONValue) json_devicelist = NULL;
> +    virNodeDeviceDefPtr *outdevs = NULL;
> +    size_t noutdevs = 0;
> +    size_t i, j;
> +
> +    json_devicelist = virJSONValueFromString(jsonstring);
> +
> +    if (!json_devicelist)
> +        goto parsefailure;
> +
> +    if (!virJSONValueIsArray(json_devicelist))
> +        goto parsefailure;
> +
> +    n = virJSONValueArraySize(json_devicelist);
> +
> +    for (i = 0; i < n; i++) {
> +        virJSONValuePtr obj = virJSONValueArrayGet(json_devicelist, i);
> +        const char *parent;
> +        virJSONValuePtr child_array;
> +        int nchildren;
> +
> +        if (!virJSONValueIsObject(obj))
> +            goto parsefailure;
> +
> +        /* mdevctl returns an array of objects.  Each object is a parent device
> +         * object containing a single key-value pair which maps from the name
> +         * of the parent device to an array of child devices */
> +        if (virJSONValueObjectKeysNumber(obj) != 1)
> +            goto parsefailure;
> +
> +        parent = virJSONValueObjectGetKey(obj, 0);
> +        child_array = virJSONValueObjectGetValue(obj, 0);
> +
> +        if (!virJSONValueIsArray(child_array))
> +            goto parsefailure;
> +
> +        nchildren = virJSONValueArraySize(child_array);
> +
> +        for (j = 0; j < nchildren; j++) {
> +            g_autoptr(virNodeDeviceDef) child = NULL;
> +            virJSONValuePtr child_obj = virJSONValueArrayGet(child_array, j);
> +
> +            if (!(child = nodeDeviceParseMdevctlChildDevice(parent, child_obj)))
> +                goto parsefailure;
> +
> +            if (VIR_APPEND_ELEMENT(outdevs, noutdevs, child) < 0)
> +                goto parsefailure;
> +        }
> +    }
> +
> +    *devs = outdevs;
> +    return noutdevs;
> +
> + parsefailure:
> +    for (i = 0; i < noutdevs; i++)
> +        virNodeDeviceDefFree(outdevs[i]);
> +    VIR_FREE(outdevs);
> +
> +    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                   _("unable to parse JSON response"));

This error message is horrible for debugging as it tells us nothing
about what part of parsing failed. Please report error messages at
the original site of the error

> +    return -1;
> +}

Regards,
Daniel
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