KVM: PPC: Book3S PR: Manage single-step mode

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@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 95bceca8f40e870fe933e3f6744b250326fca7a5..8129b0db131edfd1532bbd487097c43974baf04a 100644 (file)
--- 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. */