[PATCH] kvm-pr: manage single-step mode

Laurent Vivier
2016-03-22T14:53:58Z

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>
---
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;
+ }
break;
default:
{
@@ -1479,6 +1502,8 @@ 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 +1526,8 @@ 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. */

--
2.5.0