From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752556AbcEKLtY (ORCPT ); Wed, 11 May 2016 07:49:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:48085 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752011AbcEKLtX (ORCPT ); Wed, 11 May 2016 07:49:23 -0400 Subject: Re: [PATCH] kvm-pr: manage illegal instructions To: Laurent Vivier , kvm@vger.kernel.org, kvm-ppc@vger.kernel.org References: <1458073117-24652-1-git-send-email-lvivier@redhat.com> <57330AFE.1050209@suse.de> Cc: Michael Ellerman , Benjamin Herrenschmidt , Gleb Natapov , linuxppc-dev@lists.ozlabs.org, Paolo Bonzini , Paul Mackerras , linux-kernel@vger.kernel.org From: Alexander Graf Message-ID: <57331C3F.2000708@suse.de> Date: Wed, 11 May 2016 13:49:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>> --- >>> 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. Alex