From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: [PATCH] KVM: PPC: Fix illegal opcode emulation in kvm-pr Date: Thu, 19 May 2016 10:05:52 +0200 Message-ID: <573D73E0.90603@suse.de> References: <1463598080-27643-1-git-send-email-thuth@redhat.com> <4d984f52-16e6-8429-4b51-85f3c68fa3bc@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Laurent Vivier , Thomas Huth , Paul Mackerras , kvm-ppc@vger.kernel.org Return-path: Received: from mx2.suse.de ([195.135.220.15]:38731 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753921AbcESIFy (ORCPT ); Thu, 19 May 2016 04:05:54 -0400 In-Reply-To: <4d984f52-16e6-8429-4b51-85f3c68fa3bc@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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 >> --- >> 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. Alex