On Thu, Jun 4, 2020 at 3:37 PM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > triggered. The guest does run, but the whine (unexpected interrupt) is > > annoying and it seems to be hindering the performance drastically - of > > both the host and the guest. This behavior can even lead to the host > > watchdog biting as the firing timer prevents the progress, especially > > during the very early boot when the guest is doing heavy paging > > anyway. > > The only system I witnessed this was a Cavium TX1. It seems incredibly > bad at retiring an interrupt that has been masked at the source. > Which hardware is that? Unreleased one > > Based on the comment in the latest code the fundamental issue is that > > the interrupt controller does not recognize the timer disable fast > > enough on guest exit. > > > > Has anyone worked on a proper fix for the issue > > for the old stable series? 5+ kernels seem to have quite a drastic > > rework on this front. Plain 'isb' did not seem to do the trick after > > the timer disable... > > ISB really has no bearing on how an interrupt gets retired from the > redistributor. The flow we use on mainline these days makes it less > susceptible to this kind of brokenness, but it is still possible to > hit it. Thanks. I'll try to see if I can backport some of that. That said, if you remember my previous email, we got the kernel external hypervisor going. I have multiple kernel versions running OK (4.9 ... 5.4) under the external hypervisor. It will still need some polishing rounds and security related work, but in general it seems to run fine. 95%+ of the kvmarm code is intact and I suppose if this kind of thing is of interest to others, we could present the work and potentially some of the hooks required in the kvm code to make it all run for others, too. The guest and the host can both be VMs and the guests can be just untouchable holes in the host memory. Kind of like AMD SEV, just no encryption needed. -- Janne _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
