[PATCH v2 14/20] migration/multifd: Enable DSA offloading in multifd sender path.

[Hao Xiang]

Multifd sender path gets an array of pages queued by the migration
thread. It performs zero page checking on every page in the array.
The pages are classfied as either a zero page or a normal page. This
change uses Intel DSA to offload the zero page checking from CPU to
the DSA accelerator. The sender thread submits a batch of pages to DSA
hardware and waits for the DSA completion thread to signal for work
completion.

Signed-off-by: Hao Xiang <hao.xi...@bytedance.com>
---
 migration/multifd.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index 68ab97f918..2f635898ed 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -560,6 +560,8 @@ void multifd_save_cleanup(void)
             qemu_thread_join(&p->thread);
         }
     }
+    dsa_stop();
+    dsa_cleanup();
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
         Error *local_err = NULL;
@@ -702,6 +704,7 @@ static void buffer_is_zero_use_cpu(MultiFDSendParams *p)
 {
     const void **buf = (const void **)p->addr;
     assert(!migrate_use_main_zero_page());
+    assert(!dsa_is_running());
 
     for (int i = 0; i < p->pages->num; i++) {
         p->batch_task->results[i] = buffer_is_zero(buf[i], p->page_size);
@@ -710,15 +713,29 @@ static void buffer_is_zero_use_cpu(MultiFDSendParams *p)
 
 static void set_normal_pages(MultiFDSendParams *p)
 {
+    assert(migrate_use_main_zero_page());
+
     for (int i = 0; i < p->pages->num; i++) {
         p->batch_task->results[i] = false;
     }
 }
 
+static void buffer_is_zero_use_dsa(MultiFDSendParams *p)
+{
+    assert(!migrate_use_main_zero_page());
+    assert(dsa_is_running());
+
+    buffer_is_zero_dsa_batch_async(p->batch_task,
+                                   (const void **)p->addr,
+                                   p->pages->num,
+                                   p->page_size);
+}
+
 static void multifd_zero_page_check(MultiFDSendParams *p)
 {
     /* older qemu don't understand zero page on multifd channel */
     bool use_multifd_zero_page = !migrate_use_main_zero_page();
+    bool use_multifd_dsa_accel = dsa_is_running();
 
     RAMBlock *rb = p->pages->block;
 
@@ -726,7 +743,9 @@ static void multifd_zero_page_check(MultiFDSendParams *p)
         p->addr[i] = (ram_addr_t)(rb->host + p->pages->offset[i]);
     }
 
-    if (use_multifd_zero_page) {
+    if (use_multifd_dsa_accel && use_multifd_zero_page) {
+        buffer_is_zero_use_dsa(p);
+    } else if (use_multifd_zero_page) {
         buffer_is_zero_use_cpu(p);
     } else {
         // No zero page checking. All pages are normal pages.
@@ -1001,11 +1020,15 @@ int multifd_save_setup(Error **errp)
     int thread_count;
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
 
     if (!migrate_multifd()) {
         return 0;
     }
 
+    dsa_init(dsa_parameter);
+    dsa_start();
+
     thread_count = migrate_multifd_channels();
     multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
     multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
@@ -1061,6 +1084,7 @@ int multifd_save_setup(Error **errp)
             return ret;
         }
     }
+
     return 0;
 }
 
@@ -1138,6 +1162,8 @@ void multifd_load_cleanup(void)
 
         qemu_thread_join(&p->thread);
     }
+    dsa_stop();
+    dsa_cleanup();
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDRecvParams *p = &multifd_recv_state->params[i];
 
@@ -1272,6 +1298,7 @@ int multifd_load_setup(Error **errp)
     int thread_count;
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
 
     /*
      * Return successfully if multiFD recv state is already initialised
@@ -1281,6 +1308,9 @@ int multifd_load_setup(Error **errp)
         return 0;
     }
 
+    dsa_init(dsa_parameter);
+    dsa_start();
+
     thread_count = migrate_multifd_channels();
     multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
     multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
@@ -1317,6 +1347,7 @@ int multifd_load_setup(Error **errp)
             return ret;
         }
     }
+
     return 0;
 }
 
-- 
2.30.2