Guest hangs have been observed recently on POWER9 hosts, specifically LC92x "Boston" systems, when the guests are being rebooted multiple times. The issue isn't POWER9 specific though. It is caused by a very long standing bug when using the uncommon accel=kvm,kernel-irqchip=off machine configuration which happens to be enforced on LC92x because of a host FW limitation. This affects both the XICS and XIVE emulated interrupt controllers.
The actual fix is in patch 1. Patch 2 is a followup cleanup. The other patches are unrelated cleanups I came up with while investigating. Since this bug always existed and we're already in rc4, I think it is better to fix it in 5.0 and possibly backport it to stable and downstream if needed. -- Greg --- Greg Kurz (4): ppc: Deassert the external interrupt pin in KVM on reset xics: Don't deassert outputs ppc: Don't use CPUPPCState::irq_input_state with modern Book3s CPU models ppc: Ignore the CPU_INTERRUPT_EXITTB interrupt with KVM hw/intc/xics.c | 3 --- hw/ppc/ppc.c | 24 ++++++++++-------------- include/hw/ppc/ppc.h | 2 ++ target/ppc/cpu.h | 4 +++- target/ppc/helper_regs.h | 5 +++++ target/ppc/translate_init.inc.c | 1 + 6 files changed, 21 insertions(+), 18 deletions(-)