On 19.05.2016 10:05, Alexander Graf wrote: > On 05/19/2016 09:58 AM, Laurent Vivier wrote: >> >> On 18/05/2016 21:01, Thomas Huth wrote: >>> If kvmppc_handle_exit_pr() calls kvmppc_emulate_instruction() to emulate >>> one instruction (in the BOOK3S_INTERRUPT_H_EMUL_ASSIST case), it calls >>> kvmppc_core_queue_program() afterwards if kvmppc_emulate_instruction() >>> returned EMULATE_FAIL, so the guest gets an program interrupt for the >>> illegal opcode. >>> However, the kvmppc_emulate_instruction() also tried to inject a >>> program exception for this already, so the program interrupt gets >>> injected twice and the return address in srr0 gets destroyed. >>> All other callers of kvmppc_emulate_instruction() are also injecting >>> a program interrupt, and since the callers have the right knowledge >>> about the srr1 flags that should be used, it is the function >>> kvmppc_emulate_instruction() that should _not_ inject program >>> interrupts, so remove the kvmppc_core_queue_program() here. >>> >>> This fixes the issue discovered by Laurent Vivier with kvm-unit-tests >>> where the logs are filled with these messages when the test tries >>> to execute an illegal instruction: >>> >>> Couldn't emulate instruction 0x00000000 (op 0 xop 0) >>> kvmppc_handle_exit_pr: emulation at 700 failed (00000000) >>> >>> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> >>> --- >>> arch/powerpc/kvm/emulate.c | 1 - >>> 1 file changed, 1 deletion(-) >>> >>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c >>> index 5cc2e7a..b379146 100644 >>> --- a/arch/powerpc/kvm/emulate.c >>> +++ b/arch/powerpc/kvm/emulate.c >>> @@ -302,7 +302,6 @@ 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)); >>> - kvmppc_core_queue_program(vcpu, 0); >>> } >>> } >>> >> I've tested this patch with kvm-unit-tests: it solves the multiple >> illegal instruction exceptions, but the test fails because SRR1 is not >> updated correctly. It should contains the bit for "Illegal Instruction" >> whereas it is 0. >> [But I think it's what you explain in your last email] > > So if the illegal instruction flag is missing, that's probably because > the host CPU didn't pass that in via SRR1. That's probably a subtle > difference between EMUL_ASSIST and PROGRAM. Thanks for that hint! You're right, flags is only 0 if exit_nr is BOOK3S_INTERRUPT_H_EMUL_ASSIST. It seems to contain proper values for BOOK3S_INTERRUPT_PROGRAM, e.g. for privileged-instruction program interrupts. Looking at the PowerISA, this also supports this theory: For emulation assist interrupts, the bits in SRR1 are 0. So the right fix really seems to be to set flags = SRR1_PROGILL in case the function has been called with EMUL_ASSIST. > Please send a follow-up patch that sets the illegal instruction bit in > flags on EMULATE_FAIL as well. I think I'll best send a separate patch, since it is a separate issue. Thomas -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
