Hi Qian, On Tue, Apr 07, 2020 at 11:36:05AM -0400, Qian Cai wrote: > After further testing, the change along is insufficient. What I am chasing > right > now is the swap device will go offline after heavy memory pressure below. The > symptom is similar to what we have in the commit, > > 754265bcab78 (“iommu/amd: Fix race in increase_address_space()”) > > Apparently, it is no possible to take the domain->lock in fetch_pte() because > it > could sleep.
Thanks a lot for finding and tracking down another race in the AMD IOMMU page-table code. The domain->lock is a spin-lock and taking it can't sleep. But fetch_pte() is a fast-path and must not take any locks. I think the best fix is to update the pt_root and mode of the domain atomically by storing the mode in the lower 12 bits of pt_root. This way they are stored together and can be read/write atomically. Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu