09/07/2019 16:37, Burakov, Anatoly: > My view would be to always run in IOVA as VA by default and only falling > back to IOVA as PA if there is a need to do that. Yet, it seems that > whenever i try to bring this up, the response (not necessarily from you, > so this is not directed at you specifically) seems to be that because of > hotplug, we have to start in the "safest" (from device support point of > view) mode - that is, in IOVA as PA. Seeing how, as you claim, some > devices require IOVA as VA, then IOVA as PA is no longer the "safe" > default that all devices will support. Perhaps we can use this > opportunity to finally make IOVA as VA the default :)
That's a good point Anatoly. We need to decide what is the safest default. About the capabilities flags, please let's agree that we want to express 3 cases, so we need 2 flags. About the preference of a mode for a device, if a mode is really bad for a device, I suggest to not advertise it in capabilities. In order to take a better decision, we need a summary of the decision algorithm per layer, involving kernel driver capabilities and memory capabilities.
