On Fri, 2013-02-22 at 11:04 +1100, David Gibson wrote: > 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: > [snip] > > > > 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.
A group is an association of devices based on isolation and visibility. The dma window happens to be associated with a group on your platform, but that's not always the case. This is why I was hoping something in sysfs already reported the dma window so that we could point to it rather than creating an interface where it doesn't really belong. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
