Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757567AbcDHGXP (ORCPT ); Fri, 8 Apr 2016 02:23:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53648 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752616AbcDHGXN (ORCPT ); Fri, 8 Apr 2016 02:23:13 -0400 Subject: Re: [PATCH] kvm-pr: manage single-step mode To: Laurent Vivier , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org References: <1458658428-19566-1-git-send-email-lvivier@redhat.com> Cc: Gleb Natapov , Paolo Bonzini , Alexander Graf , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dgibson@redhat.com From: Thomas Huth Message-ID: <57074E45.4040204@redhat.com> Date: Fri, 8 Apr 2016 08:23:01 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <1458658428-19566-1-git-send-email-lvivier@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2105 Lines: 64 On 22.03.2016 15:53, Laurent Vivier wrote: > Until now, when we connect gdb to the QEMU gdb-server, the > single-step mode is not managed. > > This patch adds this, only for kvm-pr: > > If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the > MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after. > In kvmppc_handle_exit_pr, instead of routing the interrupt to > the guest, we return to host, with KVM_EXIT_DEBUG reason. > > Signed-off-by: Laurent Vivier > --- > arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++-- > 1 file changed, 29 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c > index 95bceca..e6896f4 100644 > --- a/arch/powerpc/kvm/book3s_pr.c > +++ b/arch/powerpc/kvm/book3s_pr.c > @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr) > } > #endif > > +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu) > +{ > + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { > + u64 msr = kvmppc_get_msr(vcpu); > + > + kvmppc_set_msr(vcpu, msr | MSR_SE); > + } > +} > + > +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu) > +{ > + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { > + u64 msr = kvmppc_get_msr(vcpu); > + > + kvmppc_set_msr(vcpu, msr & ~MSR_SE); > + } > +} > + > int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu, > unsigned int exit_nr) > { > @@ -1208,8 +1226,13 @@ program_interrupt: > #endif > case BOOK3S_INTERRUPT_MACHINE_CHECK: > case BOOK3S_INTERRUPT_TRACE: > - kvmppc_book3s_queue_irqprio(vcpu, exit_nr); > - r = RESUME_GUEST; > + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { > + run->exit_reason = KVM_EXIT_DEBUG; > + r = RESUME_HOST; > + } else { > + kvmppc_book3s_queue_irqprio(vcpu, exit_nr); > + r = RESUME_GUEST; > + } Should the new code rather be limited to the BOOK3S_INTERRUPT_TRACE case only? I mean, this way, you never can deliver a machine check interrupt to the guest if singlestep debugging is enabled on the host, can you? Thomas