On Fri, 8 Apr 2016 18:05:00 +0200
Laurent Vivier <lvivier@xxxxxxxxxx> 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 <lvivier@xxxxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
> v2: split BOOK3S_INTERRUPT_MACHINE_CHECK and BOOK3S_INTERRUPT_TRACE
>
> arch/powerpc/kvm/book3s_pr.c | 32 +++++++++++++++++++++++++++++++-
> 1 file changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 95bceca..8129b0d 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)
> {
> @@ -1207,10 +1225,18 @@ program_interrupt:
> break;
> #endif
> case BOOK3S_INTERRUPT_MACHINE_CHECK:
> - case BOOK3S_INTERRUPT_TRACE:
> kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> r = RESUME_GUEST;
> break;
> + case BOOK3S_INTERRUPT_TRACE:
> + 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;
> + }
> + break;
> default:
> {
> ulong shadow_srr1 = vcpu->arch.shadow_srr1;
> @@ -1479,6 +1505,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> goto out;
> }
>
> + kvmppc_setup_debug(vcpu);
> +
> /*
> * Interrupts could be timers for the guest which we have to inject
> * again, so let's postpone them until we're in the guest and if we
> @@ -1501,6 +1529,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
>
> ret = __kvmppc_vcpu_run(kvm_run, vcpu);
>
> + kvmppc_clear_debug(vcpu);
> +
> /* No need for kvm_guest_exit. It's done in handle_exit.
> We also get here with interrupts enabled. */
>
> --
> 2.5.5
>
--
David Gibson <dgibson@xxxxxxxxxx>
Senior Software Engineer, Virtualization, Red Hat
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