aarch64: virtio-keyboard-pci, interrupt-driven keyboard input (item 4.3.5e)

Punch list §25 item 4.3.5e complete.

Extended virtio_input.c with a GIC-routed interrupt path alongside 4.3.5c's
PLIC one -- same capability walk, feature negotiation, eventq handling
(confirming §27.5.1's prediction that these items would share most of the
driver). aarch64_irq_handler() dispatches to virtio_input_isr() before its
EOIR write, same claim-dispatch-complete ordering riscv64 uses. Verified
with a real QEMU sendkey keypress: exact KEY_A/press match, two real
interrupts serviced, identical result to riscv64. Found (not fixed) an
unrelated pre-existing bug: BYE's cold-reset path faults on aarch64,
discovered incidentally since nobody had exercised it from a monitored
session before. Three-arch acceptance boot clean.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/starkernel/arch/aarch64/interrupts.c

@@ -33,6 +33,14 @@ extern uint32_t apic_timer_ppi(void);
 extern void     apic_eoi_intid(uint32_t intid);
 extern void     apic_timer_rearm(void);
 
+/* Defined in virtio_input.c (item 4.3.5e). g_virtio_input_gic_intid is 0
+ * (not a valid SPI INTID -- SPIs start at 32) until
+ * virtio_input_find_keyboard() finds a real device and computes its routed
+ * INTID, so this branch is inert on any boot where the device isn't
+ * present. Same extern-in-place convention as the rest of this file. */
+extern uint32_t g_virtio_input_gic_intid;
+extern void     virtio_input_isr(void);
+
 /* INTID 1023 = "spurious" (GICv2 spec): the CPU interface has nothing
  * pending, typically because another interrupt at the same or higher
  * priority raced this one to acknowledgement. Architecturally defined,
@@ -64,6 +72,13 @@ extern void     apic_timer_rearm(void);
  * the rest of the dispatch means a fault in @c heartbeat_tick() cannot
  * also cost the next tick — same discipline as @c riscv64_timer_rearm()
  * (item 0.3).
+ *
+ * virtio-input (item 4.3.5e, @c g_virtio_input_gic_intid): dispatched
+ * **before** the @c GICC_EOIR write below, not after — the ISR itself is
+ * what deasserts the device's (level-triggered) interrupt line by reading
+ * its ISR-status capability; EOI'ing first would let the GIC immediately
+ * re-signal a still-asserted line. Same claim-dispatch-complete ordering
+ * @c riscv64_interrupt_handler() uses for its own PLIC-routed devices.
  */
 void aarch64_irq_handler(void)
 {
@@ -74,6 +89,10 @@ void aarch64_irq_handler(void)
         heartbeat_tick();
     }
 
+    if (intid == g_virtio_input_gic_intid) {
+        virtio_input_isr();
+    }
+
     if (intid != GIC_INTID_SPURIOUS) {
         apic_eoi_intid(intid);
     }

src/starkernel/virtio/virtio_input.c

@@ -1,5 +1,6 @@
 /*
- * virtio_input.c — Virtio 1.0 input device driver for StarKernel (item 4.3.5c)
+ * virtio_input.c — Virtio 1.0 input device driver for StarKernel
+ * (riscv64: item 4.3.5c; aarch64: item 4.3.5e)
  *
  * Modern virtio 1.0 interface only (device ID 0x1052). No legacy fallback
  * exists for virtio-input (unlike virtio-blk's 0x1001) -- input postdates
@@ -9,20 +10,24 @@
  * buffers: unlike virtio_blk.c's synchronous request/response pattern, the
  * driver posts empty VirtioInputEvent buffers up front and the device
  * fills+posts them to the used ring asynchronously, signalled by the PLIC
- * (see virtio_input_isr(), called from arch/riscv64/interrupts.c on a
- * matching claim) -- no polling anywhere in this path.
+ * (riscv64) or GIC (aarch64) -- see virtio_input_isr(), called from
+ * arch/riscv64/interrupts.c or arch/aarch64/interrupts.c on a matching
+ * claim -- no polling anywhere in this path.
  *
  * The PCI capability walker below is a deliberate duplicate of
  * virtio_blk.c's static walk_virtio_caps(), not a shared/promoted version
- * -- decided at this item rather than refactoring the working, tested
- * virtio_blk.c (FABRIC.md item 4.3.5c note, carries forward to 4.3.5e).
+ * -- decided at item 4.3.5c rather than refactoring the working, tested
+ * virtio_blk.c, carried forward here.
  *
- * Interrupt routing (PLIC source computation/enable) is riscv64-specific
- * and arch-guarded below; the capability walk, feature negotiation, and
- * queue/event handling are arch-agnostic and compiled for all three
- * targets (same idiom as pci.c itself: config-space access already
- * differs per arch internally, this file adds one more arch-guarded
- * piece on top rather than a second copy of the whole file).
+ * Interrupt routing (source computation/enable) is arch-guarded below,
+ * riscv64 (PLIC) and aarch64 (GIC) each with their own slot/pin-to-source
+ * formula (FABRIC.md §27.5.1 aarch64, §27.5.2 riscv64, both derived live
+ * from this host's own QEMU DTB, not assumed identical to each other). The
+ * capability walk, feature negotiation, and queue/event handling are
+ * arch-agnostic and compiled for all three targets (same idiom as pci.c
+ * itself: config-space access already differs per arch internally, this
+ * file adds one more arch-guarded piece on top rather than a second copy
+ * of the whole file).
  */
 
 #ifndef __STARKERNEL__
@@ -42,6 +47,12 @@
 #include "starkernel/plic.h"
 #endif
 
+#if defined(ARCH_AARCH64)
+/* Defined in arch/aarch64/apic.c (item 4.3.5d). Extern-in-place, same
+ * convention that file's own cross-file declarations already use. */
+extern void apic_spi_enable(uint32_t intid);
+#endif
+
 /* -------------------------------------------------------------------------
  * Virtio 1.0 PCI capability structures -- duplicated from virtio_blk.c
  * (see file header for why), plus VIRTIO_PCI_CAP_ISR_CFG actually used
@@ -200,6 +211,12 @@ static int            g_vinput_ready = 0;
  * real claim. Checked by arch/riscv64/interrupts.c's dispatch. */
 uint32_t g_virtio_input_plic_source = 0;
 
+/* GIC INTID (aarch64) this device's INTx routes to, computed at init. 0 is
+ * not a valid SPI INTID (SPIs start at 32), so it is likewise a safe
+ * "invalid/not found" sentinel. Checked by arch/aarch64/interrupts.c's
+ * dispatch. */
+uint32_t g_virtio_input_gic_intid = 0;
+
 /* -------------------------------------------------------------------------
  * Capability walker -- duplicated from virtio_blk.c, see file header.
  * ------------------------------------------------------------------------- */
@@ -251,11 +268,15 @@ static inline void wmb(void) {
 }
 
 /* -------------------------------------------------------------------------
- * Interrupt routing -- riscv64 (PLIC). aarch64 (GIC, item 4.3.5e) is not
- * yet implemented; the #else path reports rather than silently no-ops, so
- * a future arch attempting to use this file without adding its own
- * routing fails loudly instead of "working" with a permanently-pending,
- * never-enabled source.
+ * Interrupt routing -- riscv64 (PLIC, item 4.3.5c) and aarch64 (GIC, item
+ * 4.3.5e). Both compute their target source from the same PCI slot/pin
+ * swizzle shape (§27.5.1 aarch64, §27.5.2 riscv64) but with different base
+ * offsets and controller calls -- derived independently from each board's
+ * own DTB, not assumed identical. The #else path (amd64, which never
+ * attaches this device) reports rather than silently no-ops, so a future
+ * arch attempting to use this file without adding its own routing fails
+ * loudly instead of "working" with a permanently-pending, never-enabled
+ * source.
  * ------------------------------------------------------------------------- */
 
 #if defined(ARCH_RISCV64)
@@ -275,6 +296,23 @@ static int enable_interrupt_route(const PciDevice *pci)
     g_virtio_input_plic_source = source;
     return 0;
 }
+#elif defined(ARCH_AARCH64)
+static int enable_interrupt_route(const PciDevice *pci)
+{
+    uint8_t pin = pci_read8(pci, (uint16_t)PCI_CFG_INT_PIN);
+    if (pin < 1u || pin > 4u) {
+        console_println("virtio-input: bad/absent INT_PIN");
+        return -1;
+    }
+    uint32_t slot  = pci->device;
+    uint32_t spi   = 3u + ((slot + (uint32_t)pin - 1u) % 4u);
+    uint32_t intid = 32u + spi;
+
+    apic_spi_enable(intid);
+
+    g_virtio_input_gic_intid = intid;
+    return 0;
+}
 #else
 static int enable_interrupt_route(const PciDevice *pci)
 {
@@ -466,7 +504,8 @@ int virtio_input_find_keyboard(void) {
 
 /* -------------------------------------------------------------------------
  * Interrupt path -- called from arch/riscv64/interrupts.c on a matching
- * PLIC claim (g_virtio_input_plic_source).
+ * PLIC claim (g_virtio_input_plic_source) or arch/aarch64/interrupts.c on
+ * a matching GIC IRQ (g_virtio_input_gic_intid).
  * ------------------------------------------------------------------------- */
 
 void virtio_input_isr(void) {

src/word_source/include/keyboard_words.h

@@ -34,9 +34,10 @@
  * LAPIC spurious-vector interrupts, both since boot.
  *
  * @par VKBD-EVENT ( -- code value -1 | 0 )
- * Item 4.3.5c. Pop one decoded EV_KEY event (Linux input-event code/value
- * pair) off the virtio-input interrupt-fed ring buffer. Kernel-only,
- * riscv64-only today (virtio-keyboard-pci); no-op elsewhere.
+ * Items 4.3.5c (riscv64) / 4.3.5e (aarch64). Pop one decoded EV_KEY event
+ * (Linux input-event code/value pair) off the virtio-input interrupt-fed
+ * ring buffer. Kernel-only, riscv64/aarch64 (virtio-keyboard-pci); no-op
+ * on amd64 (i8042 hardware instead, see KBD-SCAN).
  *
  * @par VKBD-DEBUG ( -- isr_count )
  * Standing diagnostic: count of virtio-input ISR invocations since boot.

src/word_source/keyboard_words.c

@@ -17,7 +17,7 @@
 #include "starkernel/i8042.h"
 #endif
 
-#if defined(__STARKERNEL__) && defined(ARCH_RISCV64)
+#if defined(__STARKERNEL__) && (defined(ARCH_RISCV64) || defined(ARCH_AARCH64))
 #include "starkernel/virtio_input.h"
 #endif
 
@@ -54,16 +54,17 @@ static void kbw_debug(VM *vm)
 #endif
 }
 
-/* VKBD-EVENT ( -- code value -1 | 0 ): item 4.3.5c, riscv64 virtio-input.
- * Pop one decoded EV_KEY event off the interrupt-fed ring buffer. Pushes
- * code and value and -1 (true) if one was available, or just 0 (false) if
- * the buffer was empty. Distinct word from KBD-SCAN rather than a shared
- * one: different device, different event shape (Linux-style code/value
- * pair vs. a raw XT scancode byte) -- convergence onto one interface is
- * item 4.3.5f's explicit job, not this one's. */
+/* VKBD-EVENT ( -- code value -1 | 0 ): item 4.3.5c (riscv64) / 4.3.5e
+ * (aarch64) virtio-input. Pop one decoded EV_KEY event off the
+ * interrupt-fed ring buffer. Pushes code and value and -1 (true) if one
+ * was available, or just 0 (false) if the buffer was empty. Distinct word
+ * from KBD-SCAN rather than a shared one: different device, different
+ * event shape (Linux-style code/value pair vs. a raw XT scancode byte) --
+ * convergence onto one interface is item 4.3.5f's explicit job, not this
+ * one's. */
 static void kbw_vevent(VM *vm)
 {
-#if defined(__STARKERNEL__) && defined(ARCH_RISCV64)
+#if defined(__STARKERNEL__) && (defined(ARCH_RISCV64) || defined(ARCH_AARCH64))
     uint16_t code;
     uint32_t value;
     if (virtio_input_pop_event(&code, &value)) {
@@ -83,7 +84,7 @@ static void kbw_vevent(VM *vm)
 extern volatile uint32_t g_virtio_input_isr_count;
 static void kbw_vdebug(VM *vm)
 {
-#if defined(__STARKERNEL__) && defined(ARCH_RISCV64)
+#if defined(__STARKERNEL__) && (defined(ARCH_RISCV64) || defined(ARCH_AARCH64))
     vm_push(vm, (cell_t)g_virtio_input_isr_count);
 #else
     vm_push(vm, 0);