linux-kernel - Re: [PATCH] kvm-pr: manage illegal instructions

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Date:	Mon, 9 May 2016 10:14:41 +0200
From:	Thomas Huth <thuth@...hat.com>
To:	Laurent Vivier <lvivier@...hat.com>, kvm-ppc@...r.kernel.org,
	kvm@...r.kernel.org, Alexander Graf <agraf@...e.com>,
	Paul Mackerras <paulus@...ba.org>
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kvm-pr: manage illegal instructions

On 21.04.2016 11:25, Thomas Huth wrote:
> On 15.03.2016 21:18, 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 <lvivier@...hat.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);
>> +			emulated = EMULATE_AGAIN;
>>  		}
>>  		break;
>>  	case 19:
>>
> 
> Tested-by: Thomas Huth <thuth@...hat.com>

Ping!

Alex, Paul, could you please pick up this patch? This patch is required
to get the kvm-unit-tests working properly with kvm-pr, so I'd be glad
if we could get this included finally...

Thanks,
 Thomas