On 20.02.20 17:31, Christoph Hellwig wrote: > On Thu, Feb 20, 2020 at 05:23:20PM +0100, Christian Borntraeger wrote: >> >From a users perspective it makes absolutely perfect sense to use the >> bounce buffers when they are NEEDED. >> Forcing the user to specify iommu_platform just because you need bounce buffers >> really feels wrong. And obviously we have a severe performance issue >> because of the indirections. > > The point is that the user should not have to specify iommu_platform. I (and Halil) agree on that. From a user perspective we want to have the right thing in the guest without any command option. The iommu_plaform thing was indeed a first step to make things work. I might mis-read Halils patch, but isnt one effect of this patch set that things WILL work without iommu_platform? > We need to make sure any new hypervisor (especially one that might require > bounce buffering) always sets it, as was a rather bogus legacy hack > that isn't extensibe for cases that for example require bounce buffering.
