kvm: qemu: Switch to new guest debug interface

This patch switches both libkvm as well as the qemu pieces over to the
new guest debug interface. It comes with full support for software-based
breakpoints (via guest code modification), hardware-assisted breakpoints
and watchpoints (x86-only so far).

Breakpoint management is done inside qemu-kvm, transparently to gdbstub
and also avoiding that the gdb frontend takes over. This allows for
running debuggers inside the guest while guest debugging it active,
because the host can cleanly tell apart host- and guest-originated
breakpoint events.

Yet improvable are x86 corner cases when using single-step ("forgotten"
debug flags on the guest's stack). And, of course, the yet empty non-x86
helper functions have to be populated.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 21 insertions, 8 deletions

diff --git a/libkvm/kvm-common.h b/libkvm/kvm-common.h
index 9dae17b4..c5beacc3 100644
--- a/libkvm/kvm-common.h
+++ b/libkvm/kvm-common.h
@@ -88,7 +88,7 @@ int handle_shutdown(kvm_context_t kvm, void *env);
 void post_kvm_run(kvm_context_t kvm, void *env);
 int pre_kvm_run(kvm_context_t kvm, void *env);
 int handle_io_window(kvm_context_t kvm);
-int handle_debug(kvm_context_t kvm, void *env);
+int handle_debug(kvm_context_t kvm, int vcpu, void *env);
 int try_push_interrupts(kvm_context_t kvm);
 
 #endif
diff --git a/libkvm/libkvm.c b/libkvm/libkvm.c
index ede64178..9d3139e9 100644
--- a/libkvm/libkvm.c
+++ b/libkvm/libkvm.c
@@ -738,9 +738,15 @@ static int handle_io(kvm_context_t kvm, struct kvm_run *run, int vcpu)
 	return 0;
 }
 
-int handle_debug(kvm_context_t kvm, void *env)
+int handle_debug(kvm_context_t kvm, int vcpu, void *env)
 {
-	return kvm->callbacks->debug(kvm->opaque, env);
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+    struct kvm_run *run = kvm->run[vcpu];
+
+    return kvm->callbacks->debug(kvm->opaque, env, &run->debug.arch);
+#else
+    return 0;
+#endif
 }
 
 int kvm_get_regs(kvm_context_t kvm, int vcpu, struct kvm_regs *regs)
@@ -937,7 +943,7 @@ again:
 			r = handle_io(kvm, run, vcpu);
 			break;
 		case KVM_EXIT_DEBUG:
-			r = handle_debug(kvm, env);
+			r = handle_debug(kvm, vcpu, env);
 			break;
 		case KVM_EXIT_MMIO:
 			r = handle_mmio(kvm, run);
@@ -982,10 +988,12 @@ int kvm_inject_irq(kvm_context_t kvm, int vcpu, unsigned irq)
 	return ioctl(kvm->vcpu_fd[vcpu], KVM_INTERRUPT, &intr);
 }
 
-int kvm_guest_debug(kvm_context_t kvm, int vcpu, struct kvm_debug_guest *dbg)
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+int kvm_set_guest_debug(kvm_context_t kvm, int vcpu, struct kvm_guest_debug *dbg)
 {
-	return ioctl(kvm->vcpu_fd[vcpu], KVM_DEBUG_GUEST, dbg);
+	return ioctl(kvm->vcpu_fd[vcpu], KVM_SET_GUEST_DEBUG, dbg);
 }
+#endif
 
 int kvm_set_signal_mask(kvm_context_t kvm, int vcpu, const sigset_t *sigset)
 {
diff --git a/libkvm/libkvm.h b/libkvm/libkvm.h
index 392065ba..d068fb31 100644
--- a/libkvm/libkvm.h
+++ b/libkvm/libkvm.h
@@ -55,7 +55,10 @@ struct kvm_callbacks {
 	/// generic memory writes to unmapped memory (For MMIO devices)
     int (*mmio_write)(void *opaque, uint64_t addr, uint8_t *data,
 					int len);
-    int (*debug)(void *opaque, void *env);
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+    int (*debug)(void *opaque, void *env,
+		 struct kvm_debug_exit_arch *arch_info);
+#endif
 	/*!
 	 * \brief Called when the VCPU issues an 'hlt' instruction.
 	 *
@@ -350,7 +353,9 @@ static inline int kvm_reset_mpstate(kvm_context_t kvm, int vcpu)
  */
 int kvm_inject_irq(kvm_context_t kvm, int vcpu, unsigned irq);
 
-int kvm_guest_debug(kvm_context_t, int vcpu, struct kvm_debug_guest *dbg);
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+int kvm_set_guest_debug(kvm_context_t, int vcpu, struct kvm_guest_debug *dbg);
+#endif
 
 #if defined(__i386__) || defined(__x86_64__)
 /*!