From 2eccb107eb7dffedb4fd7efcda9528c1d95f119f Mon Sep 17 00:00:00 2001
From: Masato Imai <mii@sfc.wide.ad.jp>
Date: Fri, 13 Jun 2025 15:40:32 +0000
Subject: [PATCH] io emulation

---
 src/serial.rs   | 15 +++++++++
 src/vmm/io.rs   | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/vmm/mod.rs  |  1 +
 src/vmm/qual.rs | 12 +++----
 src/vmm/vcpu.rs | 13 +++++---
 5 files changed, 114 insertions(+), 10 deletions(-)
 create mode 100644 src/vmm/io.rs

diff --git a/src/serial.rs b/src/serial.rs
index 919ad95..cb1a4f6 100644
--- a/src/serial.rs
+++ b/src/serial.rs
@@ -1,3 +1,5 @@
+use core::fmt::Write;
+
 use lazy_static::lazy_static;
 use spin::Mutex;
 use uart_16550::SerialPort;
@@ -23,6 +25,19 @@ pub fn _print(args: ::core::fmt::Arguments) {
     });
 }
 
+#[inline(always)]
+pub fn write_byte(byte: u8) {
+    use x86_64::instructions::interrupts;
+
+    if interrupts::are_enabled() {
+        interrupts::without_interrupts(|| {
+            SERIAL1.lock().send(byte);
+        });
+    } else {
+        SERIAL1.lock().send(byte);
+    }
+}
+
 #[macro_export]
 macro_rules! serial_print {
     ($($arg:tt)*) => {
diff --git a/src/vmm/io.rs b/src/vmm/io.rs
new file mode 100644
index 0000000..455d1dd
--- /dev/null
+++ b/src/vmm/io.rs
@@ -0,0 +1,83 @@
+use x86::io::inb;
+
+use crate::{
+    serial,
+    vmm::{qual::QualIo, vcpu::VCpu},
+};
+
+#[derive(Default)]
+pub struct Serial {
+    pub ier: u8,
+    pub mcr: u8,
+}
+
+pub fn handle_io(vcpu: &mut VCpu, qual: QualIo) {
+    match qual.direction() {
+        0 => {
+            handle_io_out(vcpu, qual);
+        }
+        1 => {
+            handle_io_in(vcpu, qual);
+        }
+        _ => {}
+    }
+}
+
+pub fn handle_io_in(vcpu: &mut VCpu, qual: QualIo) {
+    let regs = &mut vcpu.guest_registers;
+    match qual.port() {
+        0x0CF8..0x0CFF => {
+            regs.rax = 0;
+        }
+        0xC000..0xCFFF => {} //ignore
+        0x03F..0x03FF => handle_serial_in(vcpu, qual),
+        _ => {
+            panic!("IO in: invalid port: {:#x}", qual.port());
+        }
+    }
+}
+
+pub fn handle_io_out(vcpu: &mut VCpu, qual: QualIo) {
+    let regs = &vcpu.guest_registers;
+    match qual.port() {
+        0x0CF8..0x0CFF => {} //ignore
+        0xC000..0xCFFF => {} //ignore
+        0x03F8..0x03FF => handle_serial_out(vcpu, qual),
+        _ => {
+            panic!("IO out: invalid port: {:#x}", qual.port());
+        }
+    }
+}
+
+fn handle_serial_in(vcpu: &mut VCpu, qual: QualIo) {
+    let regs = &mut vcpu.guest_registers;
+    match qual.port() {
+        0x3F8 => regs.rax = unsafe { inb(qual.port()).into() },
+        0x3F9 => regs.rax = vcpu.serial.ier as u64,
+        0x3FA => regs.rax = unsafe { inb(qual.port()).into() },
+        0x3FB => regs.rax = 0,
+        0x3FC => regs.rax = vcpu.serial.mcr as u64,
+        0x3FD => regs.rax = unsafe { inb(qual.port()).into() },
+        0x3FE => regs.rax = unsafe { inb(qual.port()).into() },
+        0x3FF => regs.rax = 0,
+        _ => {
+            panic!("Serial in: invalid port: {:#x}", qual.port());
+        }
+    }
+}
+
+fn handle_serial_out(vcpu: &mut VCpu, qual: QualIo) {
+    let regs = &mut vcpu.guest_registers;
+    match qual.port() {
+        0x3F8 => serial::write_byte(regs.rax as u8),
+        0x3F9 => vcpu.serial.ier = regs.rax as u8,
+        0x3FA => {}
+        0x3FB => {}
+        0x3FC => vcpu.serial.mcr = regs.rax as u8,
+        0x3FD => {}
+        0x3FF => {}
+        _ => {
+            panic!("Serial out: invalid port: {:#x}", qual.port());
+        }
+    }
+}
diff --git a/src/vmm/mod.rs b/src/vmm/mod.rs
index 0b73ad7..780a419 100644
--- a/src/vmm/mod.rs
+++ b/src/vmm/mod.rs
@@ -4,6 +4,7 @@ pub mod cr;
 pub mod ept;
 pub mod error;
 pub mod fpu;
+pub mod io;
 pub mod linux;
 pub mod msr;
 pub mod qual;
diff --git a/src/vmm/qual.rs b/src/vmm/qual.rs
index 3b01842..d24c720 100644
--- a/src/vmm/qual.rs
+++ b/src/vmm/qual.rs
@@ -131,10 +131,10 @@ bitfield! {
     pub struct QualIo(u64);
     impl Debug;
 
-    u8, size, set_size: 3, 0;
-    u8, direction, set_direction: 4, 4;
-    u8, string, set_string: 5, 5;
-    u8, rep, set_rep: 6, 6;
-    u8, operand_encoding, set_operand_encoding: 7, 7;
-    u16, port, set_port: 31, 16;
+    pub u8, size, set_size: 3, 0;
+    pub u8, direction, set_direction: 4, 4;
+    pub u8, string, set_string: 5, 5;
+    pub u8, rep, set_rep: 6, 6;
+    pub u8, operand_encoding, set_operand_encoding: 7, 7;
+    pub u16, port, set_port: 31, 16;
 }
diff --git a/src/vmm/vcpu.rs b/src/vmm/vcpu.rs
index 7ce1097..d327a4e 100644
--- a/src/vmm/vcpu.rs
+++ b/src/vmm/vcpu.rs
@@ -16,8 +16,10 @@ use crate::{
     info,
     memory::BootInfoFrameAllocator,
     vmm::{
-        cpuid, cr, fpu, msr,
-        qual::QualCr,
+        cpuid, cr, fpu,
+        io::{self, Serial},
+        msr,
+        qual::{QualCr, QualIo},
         vmcs::{
             DescriptorType, EntryControls, Granularity, PrimaryExitControls,
             PrimaryProcessorBasedVmExecutionControls, SecondaryProcessorBasedVmExecutionControls,
@@ -50,6 +52,7 @@ pub struct VCpu {
     pub ia32e_enabled: bool,
     pub xcr0: XCR0,
     pub host_xcr0: u64,
+    pub serial: Serial,
 }
 
 const TEMP_STACK_SIZE: usize = 4096;
@@ -76,6 +79,7 @@ impl VCpu {
             ia32e_enabled: false,
             xcr0: XCR0(3),
             host_xcr0: 0,
+            serial: Serial::default(),
         }
     }
 
@@ -694,7 +698,6 @@ impl VCpu {
                 _ => {}
             }
         } else {
-            info!("RIP: {:#x}", unsafe { vmread(vmcs::guest::RIP) }.unwrap());
             match info.get_reason() {
                 VmxExitReason::HLT => {
                     info!("HLT instruction executed");
@@ -730,7 +733,9 @@ impl VCpu {
                     self.step_next_inst().unwrap();
                 }
                 VmxExitReason::IO_INSTRUCTION => {
-                    info!("IO instruction executed");
+                    let qual = unsafe { vmread(vmcs::ro::EXIT_QUALIFICATION).unwrap() };
+                    let qual = QualIo(qual);
+                    io::handle_io(self, qual);
                     self.step_next_inst().unwrap();
                 }
                 _ => {