On 09-Jul-19 4:04 PM, Thomas Monjalon wrote:
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.
We do agree on this.
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.
Yes, agree with that as well.
In order to take a better decision, we need a summary of the
decision algorithm per layer, involving kernel driver capabilities
and memory capabilities.
This needs to be documented very well, as this seems to be a source of
great confusion for us all. If all was spelled out in the docs, we
wouldn't need this long discussion to figure out that we actually agree :D
--
Thanks,
Anatoly
