From patchwork Thu May 12 09:27:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 621405 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3r571d5wQ5z9t6Z for ; Thu, 12 May 2016 19:27:33 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752517AbcELJ1c (ORCPT ); Thu, 12 May 2016 05:27:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:38564 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751497AbcELJ1b (ORCPT ); Thu, 12 May 2016 05:27:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 46170AB5F; Thu, 12 May 2016 09:27:27 +0000 (UTC) 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> <57331C3F.2000708@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: <57344C7E.5010202@suse.de> Date: Thu, 12 May 2016 11:27:26 +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: Sender: kvm-ppc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org 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 >>>>> --- >>>>> 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? } } --- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html 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