>> Did that patch cause any issue, or is it just not needed on your system? >> It fixes an hypothetical problem with the way ATS is implemented. >> Maybe I actually observed it on an old software model, I don't >> remember. Either way it's unlikely to go upstream but I'd like to know >> if I should drop it from my tree. > Had to revert same patch "mm: notify remote TLBs when dirtying a PTE" to > avoid below crash[1]. I am not sure about the cause yet. I have noticed this issue earlier with patch pointed here and root caused the issue as below. It happens after vfio_mmap request from QEMU for the PCIe device and during the access of VA when PTE access flags are updated. kvm_mmu_notifier_change_pte() --> kvm_set_spte_hve() --> kvm_set_spte_hva() --> clean_dcache_guest_page() The validation model doesn't have FWB capability supported. __clean_dcache_guest_page() attempts to perform dcache flush on pcie bar address(not a valid_pfn()) through page_address(), which doesn't have page table mapping and leads to exception. I have worked around the issue by filtering out the request if the pfn is not valid in __clean_dcache_guest_page(). As the patch wasn't posted in the community, reverted it as well. -KR
