Most of this series only really affects nVMX, but there are a few x86 changes sprinkled in. Patches 1 and 2 are alternative fixes[1][2] for bugs where a #DB destined for L2 is dropped because a lower priority event, e.g. VMX preemption timer, is serviced and triggers VM-Exit, and where correctly handling the #DB can result in the preemption timer being dropped. Patch 3 fixes a semi-theoretical bug. I've been intermittently observing failures when running the preemption timer unit test in L1, but have never been able to consistently reproduce the bug. I suspect the issue is KVM_REQ_EVENT being lost, but can't really confirm this is the case due to lack of a reproducer. Patches 4-7 are cleanup/refactoring to fix non-exiting NMI/INTR priority bugs (similar to above) in patch 8. Although patch 8 is technically a bug fix, I don't think it's stable material (no sane L1 will notice), which is why I prioritized (da-dum ching) a clean implementation over an easily backported patch (a single patch would have been ugly). Patch 9 fixes a similar issue with SMI priority, and again is probably not stable material. Patch 10 addresses a gap in WARN coverage that's effectively introduced by the bug fix in patch 1. Patches 11 and 12 replace the extra call to check_nested_events() with a more precise hack-a-fix. This is a very small step towards a pipe dream of processing each event class exactly once per run loop (more below). Patch 13 is a random optimization that caught my eye when starting at this code over and over. I really, really dislike KVM's event handling flow. In the (distant) future I'd love to rework the event injection to process each event exactly once per loop, as opposed to the current behavior where check_nested_events() can be called at least twice, if not more depending on blocking behavior. That would make it much cleaner to correctly handle event prioritization and likely to maintain the code, but getting there is a significant rework with a fair number of scary changes. [1] https://lkml.kernel.org/r/20200414000946.47396-2-jmattson@xxxxxxxxxx [2] https://lkml.kernel.org/r/20200414000946.47396-1-jmattson@xxxxxxxxxx Sean Christopherson (13): KVM: nVMX: Preserve exception priority irrespective of exiting behavior KVM: nVMX: Open a window for pending nested VMX preemption timer KVM: x86: Set KVM_REQ_EVENT if run is canceled with req_immediate_exit set KVM: x86: Make return for {interrupt_nmi}_allowed() a bool instead of int KVM: nVMX: Move nested_exit_on_nmi() to nested.h KVM: nVMX: Report NMIs as allowed when in L2 and Exit-on-NMI is set KVM: VMX: Split out architectural interrupt/NMI blocking checks KVM: nVMX: Preserve IRQ/NMI priority irrespective of exiting behavior KVM: nVMX: Prioritize SMI over nested IRQ/NMI KVM: x86: WARN on injected+pending exception even in nested case KVM: VMX: Use vmx_interrupt_blocked() directly from vmx_handle_exit() KVM: x86: Replace late check_nested_events() hack with more precise fix KVM: VMX: Use vmx_get_rflags() to query RFLAGS in vmx_interrupt_blocked() arch/x86/include/asm/kvm_host.h | 6 ++- arch/x86/kvm/svm/svm.c | 10 ++-- arch/x86/kvm/vmx/nested.c | 42 +++++++++++------ arch/x86/kvm/vmx/nested.h | 5 ++ arch/x86/kvm/vmx/vmx.c | 84 +++++++++++++++++++++------------ arch/x86/kvm/vmx/vmx.h | 2 + arch/x86/kvm/x86.c | 32 +++++-------- 7 files changed, 113 insertions(+), 68 deletions(-) -- 2.26.0
