Page request: Process incoming page request

On receiving MIG_RPCOMM_REQ_PAGES look up the address and
queue the page.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

2 files changed, 115 insertions, 1 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 6ccdeb8..7d64cd3 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -21,6 +21,7 @@
 #include "sysemu/sysemu.h"
 #include "block/block.h"
 #include "qapi/qmp/qerror.h"
+#include "qapi/util.h"
 #include "qemu/sockets.h"
 #include "qemu/rcu.h"
 #include "migration/block.h"
@@ -28,9 +29,10 @@
 #include "qemu/thread.h"
 #include "qmp-commands.h"
 #include "trace.h"
-#include "qapi/util.h"
 #include "qapi-event.h"
 #include "qom/cpu.h"
+#include "exec/memory.h"
+#include "exec/address-spaces.h"
 
 #define MAX_THROTTLE  (32 << 20)      /* Migration transfer speed throttling */
 
@@ -72,6 +74,7 @@ static PostcopyState incoming_postcopy_state;
 /* For outgoing */
 MigrationState *migrate_get_current(void)
 {
+    static bool once;
     static MigrationState current_migration = {
         .state = MIGRATION_STATUS_NONE,
         .bandwidth_limit = MAX_THROTTLE,
@@ -89,6 +92,10 @@ MigrationState *migrate_get_current(void)
                 DEFAULT_MIGRATE_X_CPU_THROTTLE_INCREMENT,
     };
 
+    if (!once) {
+        qemu_mutex_init(&current_migration.src_page_req_mutex);
+        once = true;
+    }
     return &current_migration;
 }
 
@@ -771,6 +778,8 @@ static void migrate_fd_cleanup(void *opaque)
     qemu_bh_delete(s->cleanup_bh);
     s->cleanup_bh = NULL;
 
+    flush_page_queue(s);
+
     if (s->file) {
         trace_migrate_fd_cleanup();
         qemu_mutex_unlock_iothread();
@@ -903,6 +912,8 @@ MigrationState *migrate_init(const MigrationParams *params)
     s->bandwidth_limit = bandwidth_limit;
     migrate_set_state(s, MIGRATION_STATUS_NONE, MIGRATION_STATUS_SETUP);
 
+    QSIMPLEQ_INIT(&s->src_page_requests);
+
     s->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     return s;
 }
@@ -1193,7 +1204,25 @@ static struct rp_cmd_args {
 static void migrate_handle_rp_req_pages(MigrationState *ms, const char* rbname,
                                        ram_addr_t start, size_t len)
 {
+    long our_host_ps = getpagesize();
+
     trace_migrate_handle_rp_req_pages(rbname, start, len);
+
+    /*
+     * Since we currently insist on matching page sizes, just sanity check
+     * we're being asked for whole host pages.
+     */
+    if (start & (our_host_ps-1) ||
+       (len & (our_host_ps-1))) {
+        error_report("%s: Misaligned page request, start: " RAM_ADDR_FMT
+                     " len: %zd", __func__, start, len);
+        mark_source_rp_bad(ms);
+        return;
+    }
+
+    if (ram_save_queue_pages(ms, rbname, start, len)) {
+        mark_source_rp_bad(ms);
+    }
 }
 
 /*
diff --git a/migration/ram.c b/migration/ram.c
index 2e27b26..8302d09 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1016,6 +1016,91 @@ static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss,
 }
 
 /**
+ * flush_page_queue: Flush any remaining pages in the ram request queue
+ *    it should be empty at the end anyway, but in error cases there may be
+ *    some left.
+ *
+ * ms: MigrationState
+ */
+void flush_page_queue(MigrationState *ms)
+{
+    struct MigrationSrcPageRequest *mspr, *next_mspr;
+    /* This queue generally should be empty - but in the case of a failed
+     * migration might have some droppings in.
+     */
+    rcu_read_lock();
+    QSIMPLEQ_FOREACH_SAFE(mspr, &ms->src_page_requests, next_req, next_mspr) {
+        memory_region_unref(mspr->rb->mr);
+        QSIMPLEQ_REMOVE_HEAD(&ms->src_page_requests, next_req);
+        g_free(mspr);
+    }
+    rcu_read_unlock();
+}
+
+/**
+ * Queue the pages for transmission, e.g. a request from postcopy destination
+ *   ms: MigrationStatus in which the queue is held
+ *   rbname: The RAMBlock the request is for - may be NULL (to mean reuse last)
+ *   start: Offset from the start of the RAMBlock
+ *   len: Length (in bytes) to send
+ *   Return: 0 on success
+ */
+int ram_save_queue_pages(MigrationState *ms, const char *rbname,
+                         ram_addr_t start, ram_addr_t len)
+{
+    RAMBlock *ramblock;
+
+    rcu_read_lock();
+    if (!rbname) {
+        /* Reuse last RAMBlock */
+        ramblock = ms->last_req_rb;
+
+        if (!ramblock) {
+            /*
+             * Shouldn't happen, we can't reuse the last RAMBlock if
+             * it's the 1st request.
+             */
+            error_report("ram_save_queue_pages no previous block");
+            goto err;
+        }
+    } else {
+        ramblock = qemu_ram_block_by_name(rbname);
+
+        if (!ramblock) {
+            /* We shouldn't be asked for a non-existent RAMBlock */
+            error_report("ram_save_queue_pages no block '%s'", rbname);
+            goto err;
+        }
+        ms->last_req_rb = ramblock;
+    }
+    trace_ram_save_queue_pages(ramblock->idstr, start, len);
+    if (start+len > ramblock->used_length) {
+        error_report("%s request overrun start=%zx len=%zx blocklen=%zx",
+                     __func__, start, len, ramblock->used_length);
+        goto err;
+    }
+
+    struct MigrationSrcPageRequest *new_entry =
+        g_malloc0(sizeof(struct MigrationSrcPageRequest));
+    new_entry->rb = ramblock;
+    new_entry->offset = start;
+    new_entry->len = len;
+
+    memory_region_ref(ramblock->mr);
+    qemu_mutex_lock(&ms->src_page_req_mutex);
+    QSIMPLEQ_INSERT_TAIL(&ms->src_page_requests, new_entry, next_req);
+    qemu_mutex_unlock(&ms->src_page_req_mutex);
+    rcu_read_unlock();
+
+    return 0;
+
+err:
+    rcu_read_unlock();
+    return -1;
+}
+
+
+/**
  * ram_find_and_save_block: Finds a dirty page and sends it to f
  *
  * Called within an RCU critical section.