On 6/25/22 01:06, Sean Christopherson wrote:
("KVM: Replace old tlb flush function with new one to flush a specified range.") replaces old tlb flush function with kvm_flush_remote_tlbs_with_address() to do tlb flushing. However, the gfn range of tlb flushing is wrong in some cases. E.g., when a spte is dropped, the start gfn of tlb flushingHeh, "some" cases. Looks like KVM is wrong on 7 of 15 cases. And IIRC, there were already several rounds of fixes due to passing "end" instead of "nr_pages". Patches look ok on a quick read through, but I'd have to stare a bunch more to be confident. Part of me wonders if we should just revert the whole thing and then only reintroduce range-based flushing with proper testing and maybe even require performance numbers to justify the benefits. Give that almost 50% of the users are broken, it's pretty obvious that no one running KVM actually tests the behavior.
I'm pretty sure it's in use on Azure. Some of the changes are flushing less, for the others it's more than likely that Hyper-V treats a 1-page flush the same if the address points to a huge page.
Paolo
