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.
Please send a follow-up patch that sets the illegal instruction bit in flags on EMULATE_FAIL as well.
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