fix(loongarch64): Fix Virtio using too much CPU

driver/hvisor_main.c

@@ -471,6 +471,12 @@ static irqreturn_t virtio_irq_handler(int irq, void *dev_id) {
         pr_err("eventfd_signal: counter overflow or no increment\n");
 #endif
 
+#ifdef LOONGARCH64
+    /* Re-arm the level-like wakeup line after recording the eventfd kick. */
+    if (hvisor_call(HVISOR_HC_CLEAR_INJECT_IRQ, 0, HVISOR_VIRTIO_WAKEUP_HWI))
+        pr_err_ratelimited("failed to acknowledge virtio wakeup HWI\n");
+#endif
+
     return IRQ_HANDLED;
 }
 

include/hvisor.h

@@ -212,6 +212,7 @@ struct hvisor_scmi_power_args {
 
 #define HVISOR_DEASSERT_IRQ _IOW(1, 11, struct hvisor_irq_line_args)
 #define HVISOR_HC_CLEAR_INJECT_IRQ 11 // hvcall code in hvisor
+#define HVISOR_VIRTIO_WAKEUP_HWI 4    // LoongArch CPUINTC HWI2
 
 #endif /* LOONGARCH64 */
 #ifdef LOONGARCH64

tools/virtio/virtio.c

@@ -1391,14 +1391,24 @@ void handle_virtio_requests(void) {
         return;
     }
 
-    // Initial state: Mark backend as ready to receive notifications
-    __atomic_store_n(&virtio_bridge->need_wakeup, 1, memory_order_relaxed);
-
     log_info("virtio request handler loop started.");
     int signal_count = 0, proc_count = 0;
     struct epoll_event events[16];
+
+#ifdef LOONGARCH64
+    /*
+     * Drain requests that may have arrived before the event loop became ready.
+     * consume_pending_requests() also performs the sleep handshake: it sets
+     * need_wakeup, issues a full barrier, and rechecks the ring before
+     * returning.
+     */
+    proc_count += consume_pending_requests();
+#else
+    // Preserve the existing initialization behavior on other architectures.
+    __atomic_store_n(&virtio_bridge->need_wakeup, 1, memory_order_relaxed);
+#endif
+
     while (true) {
-#ifndef LOONGARCH64
         log_debug("signal_count is %d, proc_count is %d", signal_count,
                   proc_count);
 
@@ -1428,14 +1438,11 @@ void handle_virtio_requests(void) {
                 if (read(efd, &u, sizeof(uint64_t)) != sizeof(uint64_t)) {
                     continue;
                 }
-#endif
 
                 // Process all pending requests until the ring is empty
                 proc_count += consume_pending_requests();
-#ifndef LOONGARCH64
             }
         }
-#endif
     }
 }