On Wed, Aug 19, 2020 at 09:13:45PM -0600, Alex Williamson wrote:
On Thu, 20 Aug 2020 08:18:10 +0800 Yan Zhao <yan.y.zhao@intel.com> wrote:
On Wed, Aug 19, 2020 at 11:50:21AM -0600, Alex Williamson wrote: <...>
> What I care about is that we have a *standard* userspace API for > performing device compatibility checking / state migration, for use by > QEMU/libvirt/ OpenStack, such that we can write code without countless > vendor specific code paths. > > If there is vendor specific stuff on the side, that's fine as we can > ignore that, but the core functionality for device compat / migration > needs to be standardized.
To summarize: - choose one of sysfs or devlink - have a common interface, with a standardized way to add vendor-specific attributes ?
Please refer to my previous email which has more example and details. hi Parav, the example is based on a new vdpa tool running over netlink, not based on devlink, right? For vfio migration compatibility, we have to deal with both mdev and physical pci devices, I don't think it's a good idea to write a new tool for it, given we are able to retrieve the same info from sysfs and there's already an mdevctl from Alex (https://github.com/mdevctl/mdevctl).
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) - 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)
As noted previously, the parent PCI ID should not matter for an mdev device, if a vendor has a dependency on matching the parent device PCI ID, that's a vendor specific restriction. An mdev device can also expose a vfio-pci device API without the parent device being PCI. For a physical PCI device, shouldn't the PCI ID be encompassed in the signature? Thanks,
you are right. I need to put the PCI ID as a vendor specific field. I didn't do that because I wanted all fields in vendor specific to be configurable by management tools, so they can configure the target device according to the value of a vendor specific field even they don't know the meaning of the field. But maybe they can just ignore the field when they can't find a matching writable field to configure the target.
If fields can be ignored, what's the point of reporting them? Seems it's no longer a requirement. Thanks,
sorry about the confusion. I mean this condition: about to migrate, openstack searches if there are existing matching MDEVs, if yes, i.e. all common/vendor specific fields match, then just create a VM with the matching target MDEV. (in this condition, the PCI ID field is not ignored); if not, openstack tries to create one MDEV according to mdev_type, and configures MDEV according to the vendor specific attributes. as PCI ID is not a configurable field, it just ignore the field. Thanks Yan