vcpu: allow to enable/disable guest single stepping (debug)

3 files changed, 31 insertions, 0 deletions

diff --git a/examples/long_mode.rs b/examples/long_mode.rs
index 06af791..5969a48 100644
--- a/examples/long_mode.rs
+++ b/examples/long_mode.rs
@@ -181,6 +181,7 @@ fn main() -> std::io::Result<()> {
                     data
                 );
             }
+            KvmExit::Debug(_pc) => {}
         };
     }
 
diff --git a/examples/real_mode.rs b/examples/real_mode.rs
index f37d45c..fa5fb19 100644
--- a/examples/real_mode.rs
+++ b/examples/real_mode.rs
@@ -51,6 +51,7 @@ fn main() -> std::io::Result<()> {
                     data
                 );
             }
+            KvmExit::Debug(_pc) => {}
         };
     }
 
diff --git a/src/vcpu.rs b/src/vcpu.rs
index 147f602..0a3de04 100644
--- a/src/vcpu.rs
+++ b/src/vcpu.rs
@@ -108,6 +108,7 @@ impl Vcpu {
     ///
     /// [kvm-set-debugregs]:
     /// https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-set-debugregs
+    #[cfg(target_arch = "x86_64")]
     pub fn set_debugregs(&self, dregs: kvm_sys::kvm_debugregs) -> io::Result<()> {
         ioctl(
             &self.vcpu,
@@ -117,6 +118,34 @@ impl Vcpu {
         .map(|_| ())
     }
 
+    /// Enable or disable guest single steppig (debug) with the
+    /// [`KVM_GUESTDBG_ENABLE`][kvm-guest-debug] ioctl.
+    ///
+    /// [kvm-guest-debug]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-set-guest-debug
+    #[cfg(target_arch = "x86_64")]
+    pub fn set_single_step(&self, enable: bool) -> io::Result<()> {
+        let mut dbg = kvm_sys::kvm_guest_debug::default();
+
+        if enable {
+            // Enable guest debugging and single stepping.
+            dbg.control = kvm_sys::KVM_GUESTDBG_ENABLE | kvm_sys::KVM_GUESTDBG_SINGLESTEP;
+        }
+
+        // Initialize debug registers based on current VCPUs debug register values.
+        let dregs = self.get_debugregs()?;
+        dbg.arch.debugreg[0..4].copy_from_slice(&dregs.db);
+        // DR4-DR5 are reserved.
+        dbg.arch.debugreg[6] = dregs.dr6;
+        dbg.arch.debugreg[7] = dregs.dr7;
+
+        ioctl(
+            &self.vcpu,
+            kvm_sys::KVM_SET_GUEST_DEBUG,
+            &dbg as *const _ as u64,
+        )
+        .map(|_| ())
+    }
+
     /// Run the guest VCPU with the [`KVM_RUN`][kvm-run] ioctl until it exits with one of the exit
     /// reasons described in [`KvmExit`](crate::vcpu::KvmExit).
     ///