On Thu, Aug 15, 2019 at 12:09:39PM +0100, Tom Murphy wrote: > We can remove the mutex lock from amd_iommu_map and amd_iommu_unmap. > iommu_map doesn’t lock while mapping and so no two calls should touch > the same iova range. The AMD driver already handles the page table page > allocations without locks so we can safely remove the locks.
I've been looking over the code and trying to understand how the synchronization works. I gues we the cmpxchg64 in free_clear_pte is the important point here? I have to admit I don't fully understand the concurrency issues here, but neither do I understand what the mutex you removed might have helped to start with.
