[Qemu-devel] [PATCH v2 31/43] Postcopy: Create a fault handler thread before marking the ram as userfault

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/migration/migration.h |  3 +++
 postcopy-ram.c                | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 21aa8e3..98ebe69 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -87,6 +87,9 @@ struct MigrationIncomingState {
         POSTCOPY_RAM_INCOMING_END
     } postcopy_ram_state;
 
+    QemuThread     fault_thread;
+    QemuSemaphore  fault_thread_sem;
+
     QEMUFile *return_path;
     QemuMutex      rp_mutex;    /* We send replies from multiple threads */
     PostcopyPMI    postcopy_pmi;
diff --git a/postcopy-ram.c b/postcopy-ram.c
index 5b52542..84b36d7 100644
--- a/postcopy-ram.c
+++ b/postcopy-ram.c
@@ -372,8 +372,31 @@ static int postcopy_ram_sensitise_area(const char *block_name, void *host_addr,
     return 0;
 }
 
+/*
+ * Handle faults detected by the USERFAULT markings
+ */
+static void *postcopy_ram_fault_thread(void *opaque)
+{
+    MigrationIncomingState *mis = (MigrationIncomingState *)opaque;
+
+    fprintf(stderr, "postcopy_ram_fault_thread\n");
+    /* TODO: In later patch */
+    qemu_sem_post(&mis->fault_thread_sem);
+    while (1) {
+        /* TODO: In later patch */
+    }
+
+    return NULL;
+}
+
 int postcopy_ram_enable_notify(MigrationIncomingState *mis)
 {
+    /* Create the fault handler thread and wait for it to be ready */
+    qemu_sem_init(&mis->fault_thread_sem, 0);
+    qemu_thread_create(&mis->fault_thread, "postcopy/fault",
+                       postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
+    qemu_sem_wait(&mis->fault_thread_sem);
+
     /* Mark so that we get notified of accesses to unwritten areas */
     if (qemu_ram_foreach_block(postcopy_ram_sensitise_area, NULL)) {
         return -1;
-- 
1.9.3