[ -bouncing hiroshi.d...@nokia.com, +not-bouncing hd...@nvidia.com : hi Hiroshi :) ]
Hi Joerg, On Mon, Oct 10, 2011 at 11:47 AM, Roedel, Joerg <joerg.roe...@amd.com> wrote: > sorry, I was on vacation last week and had no time to look into this. Sure thing, thanks for replying! >> +#include <linux/bitmap.h> > > Is this still required? Nope, removed, thanks. > Hmm, I thought a little bit about that and came to the conculusion it > might be best to just keep the page-sizes as a part of the iommu_ops > structure. So there is no need to extend the register_iommu interface. Sure. That was one of my initial alternatives, but I decided against it at that time. I'll bring it back - it will help with the bus_set_iommu rebasing. > Also, the bus_set_iommu interface is now in the -next branch. Would be > good if you rebase the patches to that interface. Sure. It's a little tricky though: which branch do I base this on ? Are you ok with me basing this on your 'next' branch ? My current stack depends at least on three branches of yours, so that would be helpful for me (and less merging conflicts for you I guess :). > I think we need some care here and check pgsize for 0. A BUG_ON should > do. I can add it if you prefer, but I don't think it can really happen: basically, it means that we chose a too small and unsupported page bit, which can't happen as long as we check for IS_ALIGNED(iova | paddr | size, iommu_min_pagesz) in the beginning of iommu_map. >> + unmapped_order = iommu_ops->unmap(domain, iova, order); > > I think we should make sure that we call iommu_ops->unmap with the same > parameters as iommu_ops->map. Otherwise we still need some page-size > complexity in the iommu-drivers. Ok, let's discuss the semantics of ->unmap(). There isn't a clear documentation of that API (we should probably add some kernel docs after we nail it down now), but judging from the existing users (mainly kvm) and drivers, it seems that iommu_map() and iommu_unmap() aren't symmetric: users rely on unmap() to return the actual size that was unmapped. IOMMU drivers, in turn, should check which page is mapped on 'iova', unmap it, and return its size. This way iommu_unmap() becomes very simple: it just iterates through the region, relying on iommu_ops->unmap() to return the sizes that were actually unmapped (very similar to how amd's iommu_unmap_page works today). This also means that iommu_ops->unmap() doesn't really need a size/order argument and we can remove it (after all drivers fully migrate..). The other approach which you suggest means symmetric iommu_map() and iommu_unmap(). It means adding a 'paddr' parameter to iommu_unmap(), which is easy, but maybe more concerning is the limitation that it incurs: users will now have to call iommu_unmap() exactly as they called iommu_map() beforehand. Note sure how well this will fly with the existing users (kvm ?) and whether we really want to enforce this (it doesn't mean drivers need to deal with page-size complexity. they are required to unmap a single page at a time, and iommu_unmap() will do the work for them). Another discussion: I think we better change iommu_ops->map() to directly take a 'size' (in bytes) instead of an 'order' (of pages). Most (all?) drivers just immediately do 'size = 0x1000UL << gfp_order', so this whole size -> order -> size back and forth seems redundant. > When we pass the size now it makes sense to also return the > unmapped-size instead of the order. Sure. Thanks for your review, Ohad. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
