On Fri, Aug 11, 2023, Eric Wheeler wrote: > On Fri, 11 Aug 2023, Sean Christopherson wrote: > > What I suspect is happening is that the in-progress count gets left high, e.g. > > because of a start() without a paired end(), and that causes KVM to refuse to > > install mappings for the affected range of guest memory. Or possibly that the > > problematic host is generating an absolutely massive storm of invalidations and > > unintentionally DoS's the guest. > > > It would would be great to write a micro benchmark of sorts that generates > EPT page invalidation pressure, and run it on a test system inside a > virtual machine to see if we can get it to fault: > > Can you suggest the type(s) of memory operations that could be written in > user space (or kernel space as a module) to, find a test case that forces > it to fail within a reasonable period of time? Easiest thing would be to toggle PROT_EXEC via mprotect() on guest memory. KVM ignores PROT_EXEC so that guest memory doesn't need to be mapped executable in the VMM, i.e. toggling PROT_EXEC won't cause spurious failures but it will still trigger mmu_notifier invalidations. Side topic, can you provide your host Kconfig?
