From 786a195f8e81d4f7c0af2a82b9d458361d424a71 Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Wed, 26 May 2021 00:21:06 +0200
Subject: minimal KVM abstraction + real mode guest example

---
 guest/guest16.S | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 guest/guest16.S

(limited to 'guest/guest16.S')

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
-- 
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