On Wed, Aug 19, 2020 at 02:57:34PM +0800, Jason Wang wrote:
>
> On 2020/8/19 上午11:30, Yan Zhao wrote:
> > hi All,
> > could we decide that sysfs is the interface that every VFIO vendor driver
> > needs to provide in order to support vfio live migration, otherwise the
> > userspace management tool would not list the device into the compatible
> > list?
> >
> > if that's true, let's move to the standardizing of the sysfs interface.
> > (1) content
> > common part: (must)
> > - software_version: (in major.minor.bugfix scheme)
>
>
> This can not work for devices whose features can be negotiated/advertised
> independently. (E.g virtio devices)
>
sorry, I don't understand here, why virtio devices need to use vfio interface?
I think this thread is discussing about vfio related devices.
>
> > - device_api: vfio-pci or vfio-ccw ...
> > - type: mdev type for mdev device or
> > a signature for physical device which is a counterpart for
> > mdev type.
> >
> > device api specific part: (must)
> > - pci id: pci id of mdev parent device or pci id of physical pci
> > device (device_api is vfio-pci)API here.
>
>
> So this assumes a PCI device which is probably not true.
>
for device_api of vfio-pci, why it's not true?
for vfio-ccw, it's subchannel_type.
>
> > - subchannel_type (device_api is vfio-ccw)
> > vendor driver specific part: (optional)
> > - aggregator
> > - chpid_type
> > - remote_url
>
>
> For "remote_url", just wonder if it's better to integrate or reuse the
> existing NVME management interface instead of duplicating it here. Otherwise
> it could be a burden for mgmt to learn. E.g vendor A may use "remote_url"
> but vendor B may use a different attribute.
>
it's vendor driver specific.
vendor specific attributes are inevitable, and that's why we are
discussing here of a way to standardizing of it.
our goal is that mgmt can use it without understanding the meaning of vendor
specific attributes.
>
> >
> > NOTE: vendors are free to add attributes in this part with a
> > restriction that this attribute is able to be configured with the same
> > name in sysfs too. e.g.
>
>
> Sysfs works well for common attributes belongs to a class, but I'm not sure
> it can work well for device/vendor specific attributes. Does this mean mgmt
> need to iterate all the attributes in both src and dst?
>
no. just attributes under migration directory.
>
> > for aggregator, there must be a sysfs attribute in device node
> > /sys/devices/pci0000:00/0000:00:02.0/882cc4da-dede-11e7-9180-078a62063ab1/intel_vgpu/aggregator,
> > so that the userspace tool is able to configure the target device
> > according to source device's aggregator attribute.
> >
> >
> > (2) where and structure
> > proposal 1:
> > |- [path to device]
> > |--- migration
> > | |--- self
> > | | |-software_version
> > | | |-device_api
> > | | |-type
> > | | |-[pci_id or subchannel_type]
> > | | |-<aggregator or chpid_type>
> > | |--- compatible
> > | | |-software_version
> > | | |-device_api
> > | | |-type
> > | | |-[pci_id or subchannel_type]
> > | | |-<aggregator or chpid_type>
> > multiple compatible is allowed.
> > attributes should be ASCII text files, preferably with only one value
> > per file.
> >
> >
> > proposal 2: use bin_attribute.
> > |- [path to device]
> > |--- migration
> > | |--- self
> > | |--- compatible
> >
> > so we can continue use multiline format. e.g.
> > cat compatible
> > software_version=0.1.0
> > device_api=vfio_pci
> > type=i915-GVTg_V5_{val1:int:1,2,4,8}
> > pci_id=80865963
> > aggregator={val1}/2
>
>
> So basically two questions:
>
> - how hard to standardize sysfs API for dealing with compatibility check (to
> make it work for most types of devices)
sorry, I just know we are in the process of standardizing of it :)
> - how hard for the mgmt to learn with a vendor specific attributes (vs
> existing management API)
what is existing management API?
Thanks
