Messages in this thread | | | Date | Thu, 1 Jun 2023 11:06:57 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH 09/12] mm/khugepaged: retract_page_tables() without mmap or vma lock |
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On Thu, Jun 01, 2023 at 12:18:43AM +0200, Jann Horn wrote:
> 3. We have to *serialize* with page table walks performed by the > IOMMU. We're doing an RCU barrier to synchronize against page table > walks from the MMU, but without an appropriate mmu_notifier call, we > have nothing to ensure that we aren't yanking a page table out from > under an IOMMU page table walker while it's in the middle of its walk. > Sure, this isn't very likely in practice, the IOMMU page table walker > is probably pretty fast, but still we need some kind of explicit > synchronization to make this robust, I think.
There is another thread talking about this..
Broadly we are saying that we need to call mmu ops invalidate_range at any time the normal CPU TLB would be invalidated.
invalidate_range will not return until the iommu HW is coherent with the current state of the page table.
Jason
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