--- /dev/null	2026-05-03 20:55:05.750445686 +0100
+++ /mnt/data/homes/kellito/Builds/rbos/recipes/core/kernel/source/src/arch/x86_shared/device/msi.rs	2026-05-04 16:29:00.566790704 +0100
@@ -0,0 +1,165 @@
+// MSI/MSI-X support for x86 — kernel-level message composition and validation
+// Cross-referenced from Linux 7.0: arch/x86/kernel/apic/msi.c (391 lines)
+
+use crate::arch::device::local_apic::ApicId;
+
+pub const MSI_ADDRESS_BASE: u64 = 0xFEE0_0000;
+pub const MSI_ADDRESS_MASK: u64 = 0xFEEF_F000;
+const MSI_DEST_MODE_LOGICAL: u64 = 1 << 2;
+const MSI_REDIRECTION_HINT: u64 = 1 << 3;
+const MSI_DEST_MODE_PHYSICAL: u64 = 0;
+
+#[derive(Debug, Clone, Copy)]
+pub struct MsiAddress {
+    pub raw: u64,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct MsiData {
+    pub raw: u32,
+}
+
+#[derive(Debug, Clone)]
+pub struct MsiMessage {
+    pub address: MsiAddress,
+    pub data: MsiData,
+}
+
+impl MsiAddress {
+    pub fn new(dest_apic_id: u8, redirection_hint: bool, dest_mode_logical: bool) -> Self {
+        let mut addr = MSI_ADDRESS_BASE;
+        addr |= u64::from(dest_apic_id) << 12;
+        if redirection_hint { addr |= MSI_REDIRECTION_HINT; }
+        if dest_mode_logical { addr |= MSI_DEST_MODE_LOGICAL; }
+        Self { raw: addr }
+    }
+
+    pub fn validate(addr: u64) -> bool {
+        (addr & MSI_ADDRESS_MASK) == MSI_ADDRESS_BASE
+    }
+
+    pub fn dest_apic_id(&self) -> u8 {
+        ((self.raw >> 12) & 0xFF) as u8
+    }
+}
+
+impl MsiData {
+    pub fn new(vector: u8, delivery_mode: u8, trigger_mode: u8) -> Self {
+        let mut data: u32 = u32::from(vector);
+        data |= u32::from(delivery_mode) << 8;
+        data |= u32::from(trigger_mode) << 15;
+        Self { raw: data }
+    }
+
+    pub fn vector(&self) -> u8 { (self.raw & 0xFF) as u8 }
+    pub fn delivery_mode(&self) -> u8 { ((self.raw >> 8) & 0x7) as u8 }
+    pub fn trigger_mode(&self) -> u8 { ((self.raw >> 15) & 0x1) as u8 }
+}
+
+impl MsiMessage {
+    pub fn compose(dest: ApicId, vector: u8, delivery_mode: u8, trigger_mode: u8) -> Self {
+        let address = MsiAddress::new(dest.get() as u8, false, false);
+        let data = MsiData::new(vector, delivery_mode, trigger_mode);
+        Self { address, data }
+    }
+
+    pub fn validate(&self) -> bool {
+        MsiAddress::validate(self.address.raw)
+            && self.data.vector() >= 32
+            && self.data.vector() < 255
+    }
+}
+
+#[derive(Debug)]
+pub struct MsiCapability {
+    pub msg_ctl: u16,
+    pub msg_addr_lo: u32,
+    pub msg_addr_hi: u32,
+    pub msg_data: u16,
+    pub mask_bits: u32,
+    pub pending_bits: u32,
+    pub is_64bit: bool,
+    pub is_maskable: bool,
+    pub multiple_message_capable: u8,
+}
+
+impl MsiCapability {
+    pub fn parse(raw: &[u32; 6], msg_ctl: u16) -> Self {
+        Self {
+            msg_ctl,
+            msg_addr_lo: raw[1],
+            msg_addr_hi: if msg_ctl & (1 << 7) != 0 { raw[2] } else { 0 },
+            msg_data: if msg_ctl & (1 << 7) != 0 {
+                (raw[3] & 0xFFFF) as u16
+            } else {
+                (raw[2] & 0xFFFF) as u16
+            },
+            mask_bits: if msg_ctl & (1 << 8) != 0 {
+                if msg_ctl & (1 << 7) != 0 { raw[3] >> 16 } else { raw[3] }
+            } else { 0 },
+            pending_bits: if msg_ctl & (1 << 8) != 0 {
+                if msg_ctl & (1 << 7) != 0 { raw[4] } else { raw[4] }
+            } else { 0 },
+            is_64bit: msg_ctl & (1 << 7) != 0,
+            is_maskable: msg_ctl & (1 << 8) != 0,
+            multiple_message_capable: ((msg_ctl >> 1) & 0x7) as u8,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct MsixCapability {
+    pub msg_ctl: u16,
+    pub table_offset: u32,
+    pub table_bar: u8,
+    pub pba_offset: u32,
+    pub pba_bar: u8,
+    pub table_size: u16,
+}
+
+impl MsixCapability {
+    pub fn parse(raw: &[u32; 3], msg_ctl: u16) -> Self {
+        Self {
+            msg_ctl,
+            table_offset: raw[1] & !0x7,
+            table_bar: (raw[1] & 0x7) as u8,
+            pba_offset: raw[2] & !0x7,
+            pba_bar: (raw[2] & 0x7) as u8,
+            table_size: ((msg_ctl >> 1) & 0x7FF) as u16 + 1,
+        }
+    }
+}
+
+pub fn is_valid_msi_address(addr: u64) -> bool {
+    MsiAddress::validate(addr)
+}
+
+pub fn is_valid_msi_vector(vector: u8) -> bool {
+    vector >= 32 && vector < 255
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_compose_message() {
+        let msg = MsiMessage::compose(ApicId::new(0), 48, 0, 0);
+        assert!(msg.validate());
+        assert_eq!(msg.data.vector(), 48);
+    }
+
+    #[test]
+    fn test_invalid_address() {
+        assert!(!is_valid_msi_address(0xDEAD_BEEF));
+        assert!(is_valid_msi_address(0xFEE0_0000));
+    }
+
+    #[test]
+    fn test_msi_parse() {
+        let raw = [0u32; 6];
+        let cap = MsiCapability::parse(&raw, 0);
+        assert!(!cap.is_64bit);
+        assert!(!cap.is_maskable);
+    }
+}