minimal KVM abstraction + real mode guest example

1 files changed, 21 insertions, 0 deletions

diff --git a/guest/guest16.S b/guest/guest16.S
new file mode 100644
index 0000000..7f0be0e
--- /dev/null
+++ b/guest/guest16.S
@@ -0,0 +1,21 @@
+.code16
+.intel_syntax noprefix
+
+.section .boot, "ax", @progbits
+    // Trigger `KVM_EXIT_IO:KVM_EXIT_IO_OUT` by writing string to output port.
+    mov dx, 0x1000          // Output port.
+    lea si, [msg]           // Address of string.
+    mov cx, [msg_len]       // Len of string.
+    rep outsb dx, ds:[si]   // Write out string bytes.
+
+    // Trigger `KVM_EXIT_MMIO` by writing to non mapped physical address.
+    mov byte ptr ds:[0x2000], 0xaa
+
+    // Trigger `KVM_EXIT_HLT`.
+    hlt
+
+.section .rodata, "a", @progbits
+msg:
+    .asciz "Hello from Real Mode!\n"
+msg_len:
+    .byte .-msg