On 12/05/2016 11:27, Alexander Graf wrote: > On 05/12/2016 11:10 AM, Laurent Vivier wrote: >> >> On 11/05/2016 13:49, Alexander Graf wrote: >>> On 05/11/2016 01:14 PM, Laurent Vivier wrote: >>>> On 11/05/2016 12:35, Alexander Graf wrote: >>>>> On 03/15/2016 09:18 PM, Laurent Vivier wrote: >>>>>> While writing some instruction tests for kvm-unit-tests for powerpc, >>>>>> I've found that illegal instructions are not managed correctly with >>>>>> kvm-pr, >>>>>> while it is fine with kvm-hv. >>>>>> >>>>>> When an illegal instruction (like ".long 0") is processed by kvm-pr, >>>>>> the kernel logs are filled with: >>>>>> >>>>>> Couldn't emulate instruction 0x00000000 (op 0 xop 0) >>>>>> kvmppc_handle_exit_pr: emulation at 700 failed (00000000) >>>>>> >>>>>> While the exception handler receives an interrupt for each >>>>>> instruction >>>>>> executed after the illegal instruction. >>>>>> >>>>>> Signed-off-by: Laurent Vivier <lviv...@redhat.com> >>>>>> --- >>>>>> arch/powerpc/kvm/book3s_emulate.c | 4 +++- >>>>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c >>>>>> b/arch/powerpc/kvm/book3s_emulate.c >>>>>> index 2afdb9c..4ee969d 100644 >>>>>> --- a/arch/powerpc/kvm/book3s_emulate.c >>>>>> +++ b/arch/powerpc/kvm/book3s_emulate.c >>>>>> @@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, >>>>>> struct kvm_vcpu *vcpu, >>>>>> switch (get_op(inst)) { >>>>>> case 0: >>>>>> - emulated = EMULATE_FAIL; >>>>>> if ((kvmppc_get_msr(vcpu) & MSR_LE) && >>>>>> (inst == swab32(inst_sc))) { >>>>>> /* >>>>>> @@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run >>>>>> *run, >>>>>> struct kvm_vcpu *vcpu, >>>>>> kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED); >>>>>> kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4); >>>>>> emulated = EMULATE_DONE; >>>>>> + } else { >>>>>> + kvmppc_core_queue_program(vcpu, SRR1_PROGILL); >>>>> But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it >>>>> up in book3s_emulate.c is definitely the wrong spot. >>>>> >>>>> So what is the problem you're trying to solve? Is the SRR0 at the >>>>> wrong >>>>> spot or are the log messages the problem? >>>> No, the problem is the host kernel logs are filled by the message and >>>> the execution hangs. And the host becomes unresponsiveness, even after >>>> the end of the tests. >>>> >>>> Please, try to run kvm-unit-tests (the emulator test) on a KVM-PR host, >>>> and check the kernel logs (dmesg), then try to ssh to the host... >>> Ok, so the log messages are the problem. Please fix the message output >>> then - or remove it altogether. Or if you like, create a module >>> parameter that allows you to emit them. >>> >>> I personally think the best solution would be to just convert the >>> message into a trace point. >>> >>> While at it, please see whether the guest can trigger similar host log >>> output excess in other code paths. >> The problem is not really with the log messages: they are consequence of >> the bug I try to fix. >> >> What happens is once kvm_pr decodes an invalid instruction all the valid >> following instructions trigger a Program exception to the guest (but are >> executed correctly). It has no real consequence on big machine like >> POWER8, except that the guest become very slow and the log files of the >> host are filled with messages (and qemu uses 100% of the CPU). On a >> smaller machine like a PowerMac G5, the machine becomes simply unusable. > > It's probably more related to your verbosity level of kernel messages. > If you pass loglevel=0 (or quiet) to you kernel cmdline you won't get > the messages printed to serial which is what's slowing you down. > > The other problem sounds pretty severe, but the only thing your patch > does any different from the current code flow would be the patch below. > Or did I miss anything? > > diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c > index 5cc2e7a..4672bc2 100644 > --- a/arch/powerpc/kvm/emulate.c > +++ b/arch/powerpc/kvm/emulate.c > @@ -302,7 +302,11 @@ int kvmppc_emulate_instruction(struct kvm_run *run, > struct kvm_vcpu *vcpu) > advance = 0; > printk(KERN_ERR "Couldn't emulate instruction > 0x%08x " > "(op %d xop %d)\n", inst, get_op(inst), > get_xop(inst)); > +#ifdef CONFIG_PPC_BOOK3S > + kvmppc_core_queue_program(vcpu, SRR1_PROGILL); > +#else > kvmppc_core_queue_program(vcpu, 0); > +#endif > } > } >
OK, that fixes the problem. Thanks. :) Could you apply it? Laurent