On 03/02/2024 01:35, Sean Christopherson wrote: > Retry page faults without acquiring mmu_lock if the resolved gfn is covered > by an active invalidation. Contending for mmu_lock is especially > problematic on preemptible kernels as the mmu_notifier invalidation task > will yield mmu_lock (see rwlock_needbreak()), delay the in-progress > invalidation, and ultimately increase the latency of resolving the page > fault. And in the worst case scenario, yielding will be accompanied by a > remote TLB flush, e.g. if the invalidation covers a large range of memory > and vCPUs are accessing addresses that were already zapped. [...] Can confirm this patch fixes temporary guest hangs in combination with KSM and NUMA balancing I'm seeing [1], which is likely to be the same issue as described in [2]: * On this patch's base-commit 60eedcfc from git.kernel.org/pub/scm/virt/kvm/kvm.git, I can reproduce the hangs (see [1] for reproducer) * With this patch applied on top, I cannot reproduce the hangs anymore. Thanks! [1] https://lore.kernel.org/kvm/832697b9-3652-422d-a019-8c0574a188ac@xxxxxxxxxxx/ [2] https://bugzilla.kernel.org/show_bug.cgi?id=218259
