Re: [PATCH] iommu: making IOMMU sysfs nodes API public

From: David Gibson
Date: Thu Feb 21 2013 - 20:22:54 EST

On Tue, Feb 19, 2013 at 01:11:51PM -0700, Alex Williamson wrote:
> On Tue, 2013-02-19 at 18:38 +1100, David Gibson wrote:
> > On Mon, Feb 18, 2013 at 10:24:00PM -0700, Alex Williamson wrote:
> > > On Mon, 2013-02-18 at 17:15 +1100, Alexey Kardashevskiy wrote:
> > > Adding the window size to sysfs seems more readily convenient,
> > > but is it so hard for userspace to open the files and call a couple
> > > ioctls to get far enough to call IOMMU_GET_INFO? I'm unconvinced the
> > > clutter in sysfs more than just a quick fix. Thanks,
> >
> > And finally, as Alexey points out, isn't the point here so we know how
> > much rlimit to give qemu? Using ioctls we'd need a special tool just
> > to check the dma window sizes, which seems a bit hideous.
> Is it more hideous that using iommu groups to report a vfio imposed
> restriction? Are a couple open files and a handful of ioctls worse than
> code to parse directory entries and the future maintenance of an
> unrestricted grab bag of sysfs entries?

The fact that the memory is locked is a vfio restriction, but the
actual dma window size is, genuinely, a property of the group.

David Gibson | I'll have my music baroque, and my code
david AT | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!

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