Re: [PATCH v2 1/2] qmp: remove virtio_list, search QOM tree instead

[Jonah Palmer <jonah.palmer@oracle.com>]

[-- Attachment #1: Type: text/plain, Size: 10362 bytes --]

On 6/23/23 01:47, Michael S. Tsirkin wrote:

> On Fri, Jun 09, 2023 at 09:20:39AM -0400, Jonah Palmer wrote:
>> The virtio_list duplicates information about virtio devices that already
>> exist in the QOM composition tree. Instead of creating this list of
>> realized virtio devices, search the QOM composition tree instead.
>>
>> This patch modifies the QMP command qmp_x_query_virtio to instead search
>> the partial paths of '/machine/peripheral/' &
>> '/machine/peripheral-anon/' in the QOM composition tree for virtio
>> devices.
>>
>> A device is found to be a valid virtio device if (1) its canonical path
>> is of 'TYPE_VIRTIO_DEVICE' and (2) the device has been realized.
>>
>> [Jonah: In the previous commit I had written that a device is found to
>>   be a valid virtio device if (1) it has a canonical path ending with
>>   'virtio-backend'.
>>
>>   The code now determines if it's a virtio device by appending
>>   'virtio-backend' (if needed) to a given canonical path and then
>>   checking that path to see if the device is of type
>> 'TYPE_VIRTIO_DEVICE'.
>>
>>   The patch also instead now checks to make sure it's a virtio device
>>   before attempting to check whether the device is realized or not.]
>>
>> Signed-off-by: Jonah Palmer<jonah.palmer@oracle.com>
>
> Could one of QMP maintainers comment on this please?
>
>> ---
>>   hw/virtio/virtio-qmp.c | 128 ++++++++++++++++++++++++++---------------
>>   hw/virtio/virtio-qmp.h |   8 +--
>>   hw/virtio/virtio.c     |   6 --
>>   3 files changed, 82 insertions(+), 60 deletions(-)
>>
>> diff --git a/hw/virtio/virtio-qmp.c b/hw/virtio/virtio-qmp.c
>> index b5e1835299..e936cc8ce5 100644
>> --- a/hw/virtio/virtio-qmp.c
>> +++ b/hw/virtio/virtio-qmp.c
>> @@ -668,67 +668,101 @@ VirtioDeviceFeatures *qmp_decode_features(uint16_t device_id, uint64_t bitmap)
>>   VirtioInfoList *qmp_x_query_virtio(Error **errp)
>>   {
>>       VirtioInfoList *list = NULL;
>> -    VirtioInfo *node;
>> -    VirtIODevice *vdev;
>>   
>> -    QTAILQ_FOREACH(vdev, &virtio_list, next) {
>> -        DeviceState *dev = DEVICE(vdev);
>> -        Error *err = NULL;
>> -        QObject *obj = qmp_qom_get(dev->canonical_path, "realized", &err);
>> -
>> -        if (err == NULL) {
>> -            GString *is_realized = qobject_to_json_pretty(obj, true);
>> -            /* virtio device is NOT realized, remove it from list */
>> -            if (!strncmp(is_realized->str, "false", 4)) {
>> -                QTAILQ_REMOVE(&virtio_list, vdev, next);
>> -            } else {
>> -                node = g_new(VirtioInfo, 1);
>> -                node->path = g_strdup(dev->canonical_path);
>> -                node->name = g_strdup(vdev->name);
>> -                QAPI_LIST_PREPEND(list, node);
>> +    /* Query the QOM composition tree for virtio devices */
>> +    qmp_set_virtio_device_list("/machine/peripheral/", &list);
>> +    qmp_set_virtio_device_list("/machine/peripheral-anon/", &list);
> How sure are we these will forever be the only two places where virtio
> can live?

A virtio device will always be considered a peripheral device, right?
Since peripheral devices are input and/or output devices by definition.

>> +    if (list == NULL) {
>> +        error_setg(errp, "No virtio devices found");
>> +        return NULL;
>> +    }
>> +    return list;
>> +}
>> +
>> +/* qmp_set_virtio_device_list:
>> + * @ppath: An incomplete peripheral path to search from.
>> + * @list: A list of realized virtio devices.
>> + * Searches a given incomplete peripheral path (e.g. '/machine/peripheral/'
>> + * or '/machine/peripheral-anon/') for realized virtio devices and adds them
>> + * to a given list of virtio devices.
>> + */
>> +void qmp_set_virtio_device_list(const char *ppath, VirtioInfoList **list)
>> +{
>> +    ObjectPropertyInfoList *plist;
>> +    VirtioInfoList *node;
>> +    Error *err = NULL;
>> +
>> +    /* Search an incomplete path for virtio devices */
>> +    plist = qmp_qom_list(ppath, &err);
>> +    if (err == NULL) {
>> +        ObjectPropertyInfoList *start = plist;
>> +        while (plist != NULL) {
>> +            ObjectPropertyInfo *value = plist->value;
>> +            GString *path = g_string_new(ppath);
>> +            g_string_append(path, value->name);
>> +            g_string_append(path, "/virtio-backend");
>> +
>> +            /* Determine if full path is a realized virtio device */
>> +            VirtIODevice *vdev = qmp_find_virtio_device(path->str);
>> +            if (vdev != NULL) {
>> +                node = g_new0(VirtioInfoList, 1);
>> +                node->value = g_new(VirtioInfo, 1);
>> +                node->value->path = g_strdup(path->str);
>> +                node->value->name = g_strdup(vdev->name);
>> +                QAPI_LIST_PREPEND(*list, node->value);
>>               }
>> -           g_string_free(is_realized, true);
>> +            g_string_free(path, true);
>> +            plist = plist->next;
>>           }
>> -        qobject_unref(obj);
>> +        qapi_free_ObjectPropertyInfoList(start);
>>       }
>> -
>> -    return list;
>>   }
>>   
>>   VirtIODevice *qmp_find_virtio_device(const char *path)
>>   {
>> -    VirtIODevice *vdev;
>> -
>> -    QTAILQ_FOREACH(vdev, &virtio_list, next) {
>> -        DeviceState *dev = DEVICE(vdev);
>> -
>> -        if (strcmp(dev->canonical_path, path) != 0) {
>> -            continue;
>> +    Error *err = NULL;
>> +    char *basename;
>> +
>> +    /* Append 'virtio-backend' to path if needed */
>> +    basename = g_path_get_basename(path);
>> +    if (strcmp(basename, "virtio-backend")) {
>> +        GString *temp = g_string_new(path);
>> +        char *last = strrchr(path, '/');
>> +        if (g_strcmp0(last, "/")) {
>> +            g_string_append(temp, "/virtio-backend");
>> +        } else {
>> +            g_string_append(temp, "virtio-backend");
>>           }
>> +        path = g_strdup(temp->str);
>> +        g_string_free(temp, true);
>> +    }
> I don't much like the string operations. We should be able to
> check object types instead.
>
I don't either but in order for us to check if the object is a
virtio device type, we need to use the device's path ending
with '/virtio-backend'.

If there's a better method to checking this though, or perhaps
checking a different type, that doesn't involve string
manipulation, then I'm all for it.

>> -        Error *err = NULL;
>> -        QObject *obj = qmp_qom_get(dev->canonical_path, "realized", &err);
>> -        if (err == NULL) {
>> -            GString *is_realized = qobject_to_json_pretty(obj, true);
>> -            /* virtio device is NOT realized, remove it from list */
>> -            if (!strncmp(is_realized->str, "false", 4)) {
>> -                g_string_free(is_realized, true);
>> -                qobject_unref(obj);
>> -                QTAILQ_REMOVE(&virtio_list, vdev, next);
>> -                return NULL;
>> -            }
>> +    /* Verify the canonical path is a virtio device */
>> +    Object *obj = object_resolve_path(path, NULL);
>> +    if (!obj || !object_dynamic_cast(obj, TYPE_VIRTIO_DEVICE)) {
>> +        object_unref(obj);
>> +        return NULL;
>> +    }
>> +
>> +    /* Verify the virtio device is realized */
>> +    QObject *qobj = qmp_qom_get(path, "realized", &err);
>> +    if (err == NULL) {
>> +        GString *is_realized = qobject_to_json_pretty(qobj, true);
>> +        if (!strncmp(is_realized->str, "false", 4)) {
>>               g_string_free(is_realized, true);
>> -        } else {
>> -            /* virtio device doesn't exist in QOM tree */
>> -            QTAILQ_REMOVE(&virtio_list, vdev, next);
>> -            qobject_unref(obj);
>> +            qobject_unref(qobj);
>>               return NULL;
>>           }
>> -        /* device exists in QOM tree & is realized */
>> -        qobject_unref(obj);
>> -        return vdev;
>> +        g_string_free(is_realized, true);
>> +    } else {
>> +        qobject_unref(qobj);
>> +        return NULL;
>>       }
>> -    return NULL;
>> +    qobject_unref(qobj);
>> +
>> +    /* Get VirtIODevice object */
>> +    VirtIODevice *vdev = VIRTIO_DEVICE(obj);
>> +    return vdev;
>>   }
>>   
>>   VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
>> diff --git a/hw/virtio/virtio-qmp.h b/hw/virtio/virtio-qmp.h
>> index 8af5f5e65a..4b2b7875b4 100644
>> --- a/hw/virtio/virtio-qmp.h
>> +++ b/hw/virtio/virtio-qmp.h
>> @@ -15,13 +15,7 @@
>>   #include "hw/virtio/virtio.h"
>>   #include "hw/virtio/vhost.h"
>>   
>> -#include "qemu/queue.h"
>> -
>> -typedef QTAILQ_HEAD(QmpVirtIODeviceList, VirtIODevice) QmpVirtIODeviceList;
>> -
>> -/* QAPI list of realized VirtIODevices */
>> -extern QmpVirtIODeviceList virtio_list;
>> -
>> +void qmp_set_virtio_device_list(const char *ppath, VirtioInfoList **list);
>>   VirtIODevice *qmp_find_virtio_device(const char *path);
>>   VirtioDeviceStatus *qmp_decode_status(uint8_t bitmap);
>>   VhostDeviceProtocols *qmp_decode_protocols(uint64_t bitmap);
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 295a603e58..83c5db3d26 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -45,8 +45,6 @@
>>   #include "standard-headers/linux/virtio_mem.h"
>>   #include "standard-headers/linux/virtio_vsock.h"
>>   
>> -QmpVirtIODeviceList virtio_list;
>> -
>>   /*
>>    * Maximum size of virtio device config space
>>    */
>> @@ -3616,7 +3614,6 @@ static void virtio_device_realize(DeviceState *dev, Error **errp)
>>       vdev->listener.commit = virtio_memory_listener_commit;
>>       vdev->listener.name = "virtio";
>>       memory_listener_register(&vdev->listener, vdev->dma_as);
>> -    QTAILQ_INSERT_TAIL(&virtio_list, vdev, next);
>>   }
>>   
>>   static void virtio_device_unrealize(DeviceState *dev)
>> @@ -3631,7 +3628,6 @@ static void virtio_device_unrealize(DeviceState *dev)
>>           vdc->unrealize(dev);
>>       }
>>   
>> -    QTAILQ_REMOVE(&virtio_list, vdev, next);
>>       g_free(vdev->bus_name);
>>       vdev->bus_name = NULL;
>>   }
>> @@ -3805,8 +3801,6 @@ static void virtio_device_class_init(ObjectClass *klass, void *data)
>>       vdc->stop_ioeventfd = virtio_device_stop_ioeventfd_impl;
>>   
>>       vdc->legacy_features |= VIRTIO_LEGACY_FEATURES;
>> -
>> -    QTAILQ_INIT(&virtio_list);
>>   }
>>   
>>   bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)
>> -- 
>> 2.39.3

[-- Attachment #2: Type: text/html, Size: 11298 bytes --]