On 22.01.25 13:02, Alexandra Winter wrote: > > > On 22.01.25 04:04, Dust Li wrote: >> On 2025-01-20 11:28:41, Alexandra Winter wrote: >>> >>> >>> On 17.01.25 14:00, Alexandra Winter wrote: >>>> >>>> >>>> On 17.01.25 03:13, Dust Li wrote: >>>>>>>> Modular Approach: I've made the ism_loopback an independent kernel >>>>>>>> module since dynamic enable/disable functionality is not yet supported >>>>>>>> in SMC. Using insmod and rmmod for module management could provide the >>>>>>>> flexibility needed in practical scenarios. >>>>>> >>>>>> With this proposal ism_loopback is just another ism device and SMC-D will >>>>>> handle removal just like ism_client.remove(ism_dev) of other ism devices. >>>>>> >>>>>> But I understand that net/smc/ism_loopback.c today does not provide enable/disable, >>>>>> which is a big disadvantage, I agree. The ism layer is prepared for dynamic >>>>>> removal by ism_dev_unregister(). In case of this RFC that would only happen >>>>>> in case of rmmod ism. Which should be improved. >>>>>> One way to do that would be a separate ism_loopback kernel module, like you say. >>>>>> Today ism_loopback is only 10k LOC, so I'd be fine with leaving it in the ism module. >>>>>> I also think it is a great way for testing any ISM client, so it has benefit for >>>>>> anybody using the ism module. >>>>>> Another way would be e.g. an 'enable' entry in the sysfs of the loopback device. >>>>>> (Once we agree if and how to represent ism devices in genera in sysfs). >>>>> This works for me as well. I think it would be better to implement this >>>>> within the common ISM layer, rather than duplicating the code in each >>>>> device. Similar to how it's done in netdevice. >>>>> >>>>> Best regards, >>>>> Dust >>>> >>>> >>>> Is there a specific example for enable/disable in the netdevice code, you have in mind? >>>> Or do you mean in general how netdevice provides a common layer? >>>> Yes, everything that is common for all devices should be provided by the network layer. >>> >>> >>> Dust for some reason, you did not 'Reply-all': >> >> Oh, sorry I didn't notice that >> >>> Dust Li wrote: >>>> I think dev_close()/dev_open() are the high-level APIs, while >>>> ndo_stop()/ndo_open() are the underlying device operations that we >>>> can reference. >>> >>> >>> I hear you, it can be beneficial to have a way for upper layers to >>> enable/disable an ism device. >>> But all this is typically a tricky area. The device driver can also have >>> reasons to enable/disable a device, then hardware could do that or even >>> hotplug a device. Error recovery on different levels may want to run a >>> disable/enable sequence as a reset, etc. And all this has potential for >>> deadlocks. >>> All this is rather trivial for ism-loopback, as there is not much of a >>> lower layer. >>> ism-vpci already has 'HW' / device driver configure on/off and device >>> add/remove. >>> For a future ism-virtio, the Hipervisor may want to add/remove devices. >>> >>> I wonder what could be the simplest definition of an enable/disable for >>> the ism layer, that we can start with? More sophisticated functionality >>> can always be added later. >>> Maybe support for add/remove ism-device by the device driver is >>> sufficient as starting point? >> >> I agree; this can be added later. For now, we can simply support >> unregistering a device from the device driver. Which is already handled >> by ism_dev_unregister() IIUC. >> >> However, I believe we still need an API and the ability to enable or >> disable ISM devices from the upper layer. For example, if we want to >> disable a specific ISM device (such as the loopback device) in SMC, we >> should not do so by disabling the loopback device at the device layer, >> as it may also serve other clients beyond SMC. > > > Just a thought: not all clients have to use all available ism devices. > The client could opt out without removing the device. > >> >> Further more, I think removing the loopback from the loopback device >> driver seems unnecessory ? Since we should support that from the upper >> layer in the future. If it is not too much effort, I would like to have a simple remove for ism_loopback soon, as it would allow for simple variations of testcases. >> >> Best regards, >> Dust > > > All good points. But it also shows that there are many options how to > extend ism device handling of the upper layers / clients. > e.g. I can image a loop macro ism_for_each_dev() might be nice... > I'd prefer to take one step at a time. Start with a minimal useful ism > layer and extend by usecase. > > > > > > > > >
