diff --git a/vm-allocator/src/gsi.rs b/vm-allocator/src/gsi.rs
new file mode 100644
index 000000000..88e05bf8e
--- /dev/null
+++ b/vm-allocator/src/gsi.rs
@@ -0,0 +1,84 @@
+// Copyright © 2019 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause
+
+use std::collections::btree_map::BTreeMap;
+use std::result;
+
+#[derive(Debug)]
+pub enum Error {
+    Overflow,
+}
+
+pub type Result<T> = result::Result<T, Error>;
+
+/// GsiApic
+#[derive(Copy, Clone)]
+pub struct GsiApic {
+    base: u32,
+    irqs: u32,
+}
+
+impl GsiApic {
+    /// New GSI APIC
+    pub fn new(base: u32, irqs: u32) -> Self {
+        GsiApic { base, irqs }
+    }
+}
+
+/// GsiAllocator
+pub struct GsiAllocator {
+    apics: BTreeMap<u32, u32>,
+    next_irq: u32,
+    next_gsi: u32,
+}
+
+impl GsiAllocator {
+    /// New GSI allocator
+    pub fn new(apics: Vec<GsiApic>) -> Self {
+        let mut allocator = GsiAllocator {
+            apics: BTreeMap::new(),
+            next_irq: 0xffff_ffff,
+            next_gsi: 0,
+        };
+
+        for apic in &apics {
+            if apic.base < allocator.next_irq {
+                allocator.next_irq = apic.base;
+            }
+
+            if apic.base + apic.irqs > allocator.next_gsi {
+                allocator.next_gsi = apic.base + apic.irqs;
+            }
+
+            allocator.apics.insert(apic.base, apic.irqs);
+        }
+
+        allocator
+    }
+
+    /// Allocate a GSI
+    pub fn allocate_gsi(&mut self) -> Result<u32> {
+        self.next_gsi = self.next_gsi.checked_add(1).ok_or(Error::Overflow)?;
+
+        Ok(self.next_gsi - 1)
+    }
+
+    /// Allocate an IRQ
+    pub fn allocate_irq(&mut self) -> Result<u32> {
+        let mut irq: u32 = 0;
+        for (base, irqs) in self.apics.iter() {
+            // HACKHACK - This only works with 1 single IOAPIC...
+            if self.next_irq >= *base && self.next_irq < *base + *irqs {
+                irq = self.next_irq;
+                self.next_irq += 1;
+            }
+        }
+
+        if irq == 0 {
+            return Err(Error::Overflow);
+        }
+
+        Ok(irq)
+    }
+}
diff --git a/vm-allocator/src/lib.rs b/vm-allocator/src/lib.rs
index 4a14420dd..15d431ce5 100644
--- a/vm-allocator/src/lib.rs
+++ b/vm-allocator/src/lib.rs
@@ -14,7 +14,9 @@ extern crate libc;
 extern crate vm_memory;
 
 mod address;
+mod gsi;
 mod system;
 
 pub use crate::address::AddressAllocator;
+pub use crate::gsi::{GsiAllocator, GsiApic};
 pub use crate::system::SystemAllocator;
diff --git a/vm-allocator/src/system.rs b/vm-allocator/src/system.rs
index e83682540..acb8b4926 100755
--- a/vm-allocator/src/system.rs
+++ b/vm-allocator/src/system.rs
@@ -10,6 +10,7 @@
 use vm_memory::{GuestAddress, GuestUsize};
 
 use crate::address::AddressAllocator;
+use crate::gsi::{GsiAllocator, GsiApic};
 
 use libc::{sysconf, _SC_PAGESIZE};
 
@@ -25,12 +26,12 @@ fn pagesize() -> usize {
 /// # Example - Use the `SystemAddress` builder.
 ///
 /// ```
-/// # use vm_allocator::SystemAllocator;
+/// # use vm_allocator::{GsiApic, SystemAllocator};
 /// # use vm_memory::{Address, GuestAddress, GuestUsize};
 ///   let mut allocator = SystemAllocator::new(
 ///           GuestAddress(0x1000), 0x10000,
 ///           GuestAddress(0x10000000), 0x10000000,
-///           5).unwrap();
+///           vec![GsiApic::new(5, 19)]).unwrap();
 ///    assert_eq!(allocator.allocate_irq(), Some(5));
 ///    assert_eq!(allocator.allocate_irq(), Some(6));
 ///    assert_eq!(allocator.allocate_mmio_addresses(None, 0x1000, Some(0x1000)), Some(GuestAddress(0x1fffe000)));
@@ -39,7 +40,7 @@ fn pagesize() -> usize {
 pub struct SystemAllocator {
     io_address_space: AddressAllocator,
     mmio_address_space: AddressAllocator,
-    next_irq: u32,
+    gsi_allocator: GsiAllocator,
 }
 
 impl SystemAllocator {
@@ -56,23 +57,23 @@ impl SystemAllocator {
         io_size: GuestUsize,
         mmio_base: GuestAddress,
         mmio_size: GuestUsize,
-        first_irq: u32,
+        apics: Vec<GsiApic>,
     ) -> Option<Self> {
         Some(SystemAllocator {
             io_address_space: AddressAllocator::new(io_base, io_size)?,
             mmio_address_space: AddressAllocator::new(mmio_base, mmio_size)?,
-            next_irq: first_irq,
+            gsi_allocator: GsiAllocator::new(apics),
         })
     }
 
     /// Reserves the next available system irq number.
     pub fn allocate_irq(&mut self) -> Option<u32> {
-        if let Some(irq_num) = self.next_irq.checked_add(1) {
-            self.next_irq = irq_num;
-            Some(irq_num - 1)
-        } else {
-            None
-        }
+        self.gsi_allocator.allocate_irq().ok()
+    }
+
+    /// Reserves the next available GSI.
+    pub fn allocate_gsi(&mut self) -> Option<u32> {
+        self.gsi_allocator.allocate_gsi().ok()
     }
 
     /// Reserves a section of `size` bytes of IO address space.
diff --git a/vmm/src/vm.rs b/vmm/src/vm.rs
index 9b48f0abb..e322eab1b 100755
--- a/vmm/src/vm.rs
+++ b/vmm/src/vm.rs
@@ -44,7 +44,7 @@ use std::os::unix::io::{AsRawFd, RawFd};
 use std::ptr::null_mut;
 use std::sync::{Arc, Barrier, Mutex};
 use std::{result, str, thread};
-use vm_allocator::SystemAllocator;
+use vm_allocator::{GsiApic, SystemAllocator};
 use vm_memory::guest_memory::FileOffset;
 use vm_memory::{
     Address, Bytes, Error as MmapError, GuestAddress, GuestMemory, GuestMemoryMmap,
@@ -1066,13 +1066,18 @@ impl<'a> Vm<'a> {
 
         CpuidPatch::patch_cpuid(&mut cpuid, cpuid_patches);
 
+        let ioapic = GsiApic::new(
+            X86_64_IRQ_BASE,
+            ioapic::NUM_IOAPIC_PINS as u32 - X86_64_IRQ_BASE,
+        );
+
         // Let's allocate 64 GiB of addressable MMIO space, starting at 0.
         let mut allocator = SystemAllocator::new(
             GuestAddress(0),
             1 << 16 as GuestUsize,
             GuestAddress(0),
             1 << 36 as GuestUsize,
-            X86_64_IRQ_BASE,
+            vec![ioapic],
         )
         .ok_or(Error::CreateSystemAllocator)?;