diff --git a/build/qemu.rs b/build/qemu.rs
index 002c778284..d2713f48d7 100644
--- a/build/qemu.rs
+++ b/build/qemu.rs
@@ -325,7 +325,10 @@ fn machine(arch: Arch, iommu: bool) -> String {
     match (arch, iommu) {
         (Arch::X86_64, true) => format!("{base},kernel-irqchip=split"),
         (Arch::X86_64, false) => base.to_string(),
-        (Arch::Aarch64, true) => format!("{base},gic-version=3,iommu=smmuv3"),
+        // HVF's GIC has no ITS; PCI claims need QEMU's GIC to remap their messages.
+        (Arch::Aarch64, true) => {
+            format!("{base},gic-version=3,iommu=smmuv3,its=on,kernel-irqchip=off")
+        }
         (Arch::Aarch64, false) => format!("{base},gic-version=3"),
     }
 }
diff --git a/issues/the-arm-desktop-starts-with-no-keyboard-or-mouse.md b/issues/the-arm-desktop-starts-with-no-keyboard-or-mouse.md
new file mode 100644
index 0000000000..4a4ab234d4
--- /dev/null
+++ b/issues/the-arm-desktop-starts-with-no-keyboard-or-mouse.md
@@ -0,0 +1,30 @@
+---
+status: open
+kind: defect
+opened: 2026-10-11
+---
+
+# The ARM desktop starts with no keyboard or mouse
+
+An AArch64 boot of `images/system.toml` under QEMU `virt` reaches the
+supervisor and initializes virtio-gpu, but the compositor exits 101 at
+`system/compositor/src/session.rs` because its keyboard endowment is absent.
+The supervisor reports both keyboard and mouse absent. This was read in
+the owner's boot of `57616a067` and reproduced with the shipping image.
+
+The launcher attaches a USB keyboard and tablet to its xHCI. The kernel's
+xHCI driver refuses to arm on AArch64: `arch/aarch64/irqchip/its.rs::msi`
+refuses kernel drivers. Enabling the ITS makes PCI claims possible but
+does not give that driver an interrupt. `system/usbd` currently enumerates
+devices without binding their classes and is not started by the shipped
+manifest. There is no virtio-input driver.
+
+Owner: `issues/toyos-runs-on-arm64.md`, stages 6 and 7, with the userland
+USB move in `issues/the-kernel-is-small-interrupts-post-and-threads-wait.md`.
+DMA and interrupt isolation remain required.
+
+Exit: an ARM boot of the shipped manifest supplies real keyboard and mouse
+input to the compositor; injected key transitions and pointer events reach
+the desktop and an application's window in a test that fails when delivery
+is removed. The compositor starts and presents a frame without the missing
+keyboard panic.
diff --git a/kernel/src/pcidev/mod.rs b/kernel/src/pcidev/mod.rs
index acf6686f2d..5b906da80b 100644
--- a/kernel/src/pcidev/mod.rs
+++ b/kernel/src/pcidev/mod.rs
@@ -495,6 +495,11 @@ pub fn publish(devices: &[PciDevice], segment: u16, maps: &[MemoryMapEntry], fir
     let mut decoded = Vec::new();
     let mut taken: Vec<Window> =
         maps.iter().map(|entry| Window { start: entry.start, end: entry.end }).collect();
+    // ECAM decodes configuration space even when firmware lists it as free MMIO.
+    taken.extend(crate::drivers::pci::windows().into_iter().map(|ecam| {
+        let (start, bytes) = ecam.decoded();
+        Window { start, end: start.saturating_add(bytes) }
+    }));
     for device in devices {
         // Bounded by the header's own declaration: a bridge has two BAR slots
         // and four registers past them that are not BARs, and `bar_size` below
diff --git a/tests/toyos.rs b/tests/toyos.rs
index 36f92181a3..8b6f5bda81 100644
--- a/tests/toyos.rs
+++ b/tests/toyos.rs
@@ -2246,7 +2246,8 @@ fn virt_no_seed_refused(profile: qemu::Profile, test_config: &Path) -> Result<()
 
 /// A machine whose MCFG decodes sixteen buses, with RAM past them: the kernel
 /// maps those sixteen buses' megabytes and no more, and enumerates the
-/// functions QEMU put there and nothing else, and the boot goes on.
+/// functions QEMU put there and nothing else. BAR placement keeps the
+/// configuration window out of its free runs, and the boot goes on.
 fn virt_low_ecam(profile: qemu::Profile, test_config: &Path) -> Result<(), String> {
     const WINDOW: &str = "ACPI: ECAM window: segment 0 buses 0x00..=0x0f, bus 0 at 0x3f000000";
     const MAPPED: &str = "mmio: 0x3f000000+0x1000000 ";
@@ -2281,6 +2282,21 @@ fn virt_low_ecam(profile: qemu::Profile, test_config: &Path) -> Result<(), Strin
             return Err(format!("{want:?} not on the PL011\nserial:\n{serial}"));
         }
     }
+    let mut runs = 0;
+    for line in serial.lines().filter_map(|l| l.split_once("pcidev:   ").map(|(_, run)| run)) {
+        let range = line.split_whitespace().next().ok_or("an empty PCI free run")?;
+        let (start, end) = range.split_once("..").ok_or("a PCI free run without its end")?;
+        let address = |word: &str| u64::from_str_radix(word.trim_start_matches("0x"), 16)
+            .map_err(|why| format!("invalid PCI free-run address {word:?}: {why}"));
+        let (start, end) = (address(start)?, address(end)?);
+        if start < 0x4000_0000 && end > 0x3f00_0000 {
+            return Err(format!("BAR placement offers ECAM configuration space in {range}\nserial:\n{serial}"));
+        }
+        runs += 1;
+    }
+    if runs == 0 {
+        return Err(format!("the boot reported no PCI free runs\nserial:\n{serial}"));
+    }
     eprintln!("  [virt] {WINDOW}; {} functions: {found:?}", found.len());
     Ok(())
 }