On Fri, Apr 23, 2021 at 07:28:03PM -0300, Jason Gunthorpe wrote: > On Fri, Apr 23, 2021 at 10:38:51AM -0600, Alex Williamson wrote: > > On Thu, 22 Apr 2021 20:39:50 -0300 > > > > /dev/ioasid should understand the group concept somehow, otherwise it > > > is incomplete and maybe even security broken. > > > > > > So, how do I add groups to, say, VDPA in a way that makes sense? The > > > only answer I come to is broadly what I outlined here - make > > > /dev/ioasid do all the group operations, and do them when we enjoin > > > the VDPA device to the ioasid. > > > > > > Once I have solved all the groups problems with the non-VFIO users, > > > then where does that leave VFIO? Why does VFIO need a group FD if > > > everyone else doesn't? > > > > This assumes there's a solution for vDPA that doesn't just ignore the > > problem and hope for the best. I can't speak to a vDPA solution. > > I don't think we can just ignore the question and succeed with > /dev/ioasid. > > Guess it should get answered as best it can for ioasid "in general" > then we can decide if it makes sense for VFIO to use the group FD or > not when working in ioasid mode. > > Maybe a better idea will come up > > > an implicit restriction. You've listed a step in the description about > > a "list of devices in the group", but nothing in the pseudo code > > reflects that step. > > I gave it below with the readdir() - it isn't in the pseudo code > because the applications I looked through didn't use it, and wouldn't > benefit from it. I tried to show what things were doing today. And chance are they will break cryptically if you give them a device in a multi-device group. That's not something we want to encourage. > > > I expect it would be a subtly missed by any userspace driver > > developer unless they happen to work on a system where the grouping > > is not ideal. > > I'm still unclear - what are be the consequence if the application > designer misses the group detail? > > Jason > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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