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Re: [Qemu-block] [Qemu-devel] [PATCH v4 1/2] virtio: introduce `query-vi
From: |
Jan Dakinevich |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v4 1/2] virtio: introduce `query-virtio' QMP command |
Date: |
Wed, 4 Oct 2017 17:26:58 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 |
On 10/03/2017 07:29 PM, Dr. David Alan Gilbert wrote:
> * Jan Dakinevich (address@hidden) wrote:
>>
>>
>> On 10/03/2017 05:02 PM, Eric Blake wrote:
>>> On 10/03/2017 07:47 AM, Jan Dakinevich wrote:
>>>> The command is intended for gathering virtio information such as status,
>>>> feature bits, negotiation status. It is convenient and useful for debug
>>>> purpose.
>>>>
>>>> The commands returns generic virtio information for virtio such as
>>>> common feature names and status bits names and information for all
>>>> attached to current machine devices.
>>>>
>>>> To retrieve names of device-specific features `get_feature_name'
>>>> callback in VirtioDeviceClass also was introduced.
>>>>
>>>> Cc: Denis V. Lunev <address@hidden>
>>>> Signed-off-by: Jan Dakinevich <address@hidden>
>>>> ---
>>>> hw/block/virtio-blk.c | 21 +++++++++
>>>> hw/char/virtio-serial-bus.c | 15 +++++++
>>>> hw/display/virtio-gpu.c | 13 ++++++
>>>> hw/net/virtio-net.c | 35 +++++++++++++++
>>>> hw/scsi/virtio-scsi.c | 16 +++++++
>>>> hw/virtio/Makefile.objs | 2 +
>>>> hw/virtio/virtio-balloon.c | 15 +++++++
>>>> hw/virtio/virtio-stub.c | 9 ++++
>>>> hw/virtio/virtio.c | 101
>>>> ++++++++++++++++++++++++++++++++++++++++++++
>>>> include/hw/virtio/virtio.h | 2 +
>>>> qapi-schema.json | 1 +
>>>> qapi/virtio.json | 94
>>>> +++++++++++++++++++++++++++++++++++++++++
>>>> 12 files changed, 324 insertions(+)
>>>> create mode 100644 hw/virtio/virtio-stub.c
>>>> create mode 100644 qapi/virtio.json
>>>
>>> This creates a new .json file, but does not touch MAINTAINERS. Our idea
>>> in splitting the .json files was to make it easier for each sub-file
>>> that needs a specific maintainer in addition to the overall *.json line
>>> for QAPI maintainers, so this may deserve a MAINTAINERS entry.
>>>
>>
>> Ok.
>>
>>>> +++ b/qapi/virtio.json
>>>> @@ -0,0 +1,94 @@
>>>> +# -*- Mode: Python -*-
>>>> +#
>>>> +
>>>> +##
>>>> +# = Virtio devices
>>>> +##
>>>> +
>>>> +{ 'include': 'common.json' }
>>>> +
>>>> +##
>>>> +# @VirtioInfoBit:
>>>> +#
>>>> +# Named virtio bit
>>>> +#
>>>> +# @bit: bit number
>>>> +#
>>>> +# @name: bit name
>>>> +#
>>>> +# Since: 2.11.0
>>>> +#
>>>> +##
>>>> +{
>>>> + 'struct': 'VirtioInfoBit',
>>>> + 'data': {
>>>> + 'bit': 'uint64',
>>>
>>> Why is this a 64-bit value? Are the values 0-63, or are they 1, 2, 4, 8,
>>> ...? The documentation on 'bit number' is rather sparse.
>>
>> I would prefer `uint' here, but I don't see generic unsigned type (may
>> be, I am mistaken). I could use uint8 here, though.
>>
>>>
>>>> + 'name': 'str'
>>>
>>> Wouldn't an enum type be better than an open-ended string?
>>>
>>
>> Bit names are not known here, they are obtained from virtio device
>> implementations.
>>
>>>> + }
>>>> +}
>>>> +
>>>> +##
>>>> +# @VirtioInfoDevice:
>>>> +#
>>>> +# Information about specific virtio device
>>>> +#
>>>> +# @qom_path: QOM path of the device
>>>
>>> Please make this 'qom-path' - new interfaces should prefer '-' over '_'.
>>
>> Ok.
>>
>>>> +#
>>>> +# @feature-names: names of device-specific features
>>>> +#
>>>> +# @host-features: bitmask of features, provided by devices
>>>> +#
>>>> +# @guest-features: bitmask of features, acknowledged by guest
>>>> +#
>>>> +# @status: virtio device status bitmask
>>>> +#
>>>> +# Since: 2.11.0
>>>> +#
>>>> +##
>>>> +{
>>>> + 'struct': 'VirtioInfoDevice',
>>>> + 'data': {
>>>> + 'qom_path': 'str',
>>>> + 'feature-names': ['VirtioInfoBit'],
>>>> + 'host-features': 'uint64',
>>>> + 'guest-features': 'uint64',
>>>> + 'status': 'uint64'
>>>
>>> I'm wondering if this is the best representation (where the caller has
>>> to parse the integer and then lookup in feature-names what each bit of
>>> the integer represents). But I'm not sure I have anything better off
>>> the top of my head.
>>>
>>
>> Consider it as way to tell caller about names of supported features.
>>
>>>> + }
>>>> +}
>>>> +
>>>> +##
>>>> +# @VirtioInfo:
>>>> +#
>>>> +# Information about virtio devices
>>>> +#
>>>> +# @feature-names: names of common virtio features
>>>> +#
>>>> +# @status-names: names of bits which represents virtio device status
>>>> +#
>>>> +# @devices: list of per-device virtio information
>>>> +#
>>>> +# Since: 2.11.0
>>>> +#
>>>> +##
>>>> +{
>>>> + 'struct': 'VirtioInfo',
>>>> + 'data': {
>>>> + 'feature-names': ['VirtioInfoBit'],
>>>
>>> Why is feature-names listed at two different nestings of the return value?
>>>
>>
>> These are different feature names. First names are common and predefined
>> for all devices. Second names are device-specific.
>
> If you can turn these into enums (union'd enums?) then you might
> be able to get rid of a lot of your array filling/naming conversion
> boilerplate. (Not sure if it's worth it, but it's worth looking).
>
I would be happy to drop this boilerplate, but how enum could help here?
To respond my requirement it should be something like set, not enum.
Even so, having set, I would have been needed to declare mapping between
names in set type and bit numbers within feature bitmask.
> Dave
>
>>>> + 'status-names': ['VirtioInfoBit'],
>>>> + 'devices': ['VirtioInfoDevice']
>>>> + }
>>>> +}
>>>> +
>>>> +
>>>> +##
>>>> +# @query-virtio:
>>>> +#
>>>> +# Returns generic and per-device virtio information
>>>> +#
>>>> +# Since: 2.11.0
>>>> +#
>>>> +##
>>>> +{
>>>> + 'command': 'query-virtio',
>>>> + 'returns': 'VirtioInfo'
>>>> +}
>>>>
>>>
>>
>> --
>> Best regards
>> Jan Dakinevich
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
>
--
Best regards
Jan Dakinevich