[PATCH v4 10/14] migration/multifd: Enable DSA offloading in multifd sender path.

[Hao Xiang <hao.xiang@linux.dev>]

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.xiang@linux.dev>
---
 migration/multifd-zero-page.c | 99 +++++++++++++++++++++++++++++++++--
 migration/multifd.c           | 27 +++++++++-
 migration/multifd.h           |  1 +
 3 files changed, 120 insertions(+), 7 deletions(-)

diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c
index e1b8370f88..4f426289e4 100644
--- a/migration/multifd-zero-page.c
+++ b/migration/multifd-zero-page.c
@@ -37,25 +37,83 @@ static void swap_page_offset(ram_addr_t *pages_offset, int a, int b)
 }
 
 /**
- * multifd_send_zero_page_detect: Perform zero page detection on all pages.
+ * zero_page_detect_cpu: Perform zero page detection using CPU.
  *
  * Sorts normal pages before zero pages in p->pages->offset and updates
  * p->pages->normal_num.
  *
  * @param p A pointer to the send params.
  */
-void multifd_send_zero_page_detect(MultiFDSendParams *p)
+static void zero_page_detect_cpu(MultiFDSendParams *p)
 {
     MultiFDPages_t *pages = p->pages;
     RAMBlock *rb = pages->block;
     int i = 0;
     int j = pages->num - 1;
 
-    if (!multifd_zero_page_enabled()) {
-        pages->normal_num = pages->num;
+    /*
+     * Sort the page offset array by moving all normal pages to
+     * the left and all zero pages to the right of the array.
+     */
+    while (i <= j) {
+        uint64_t offset = pages->offset[i];
+
+        if (!buffer_is_zero(rb->host + offset, p->page_size)) {
+            i++;
+            continue;
+        }
+
+        swap_page_offset(pages->offset, i, j);
+        ram_release_page(rb->idstr, offset);
+        j--;
+    }
+
+    pages->normal_num = i;
+}
+
+
+#ifdef CONFIG_DSA_OPT
+
+static void swap_result(bool *results, int a, int b)
+{
+    bool temp;
+
+    if (a == b) {
         return;
     }
 
+    temp = results[a];
+    results[a] = results[b];
+    results[b] = temp;
+}
+
+/**
+ * zero_page_detect_dsa: Perform zero page detection using
+ * Intel Data Streaming Accelerator (DSA).
+ *
+ * Sorts normal pages before zero pages in p->pages->offset and updates
+ * p->pages->normal_num.
+ *
+ * @param p A pointer to the send params.
+ */
+static void zero_page_detect_dsa(MultiFDSendParams *p)
+{
+    MultiFDPages_t *pages = p->pages;
+    RAMBlock *rb = pages->block;
+    bool *results = p->batch_task->results;
+
+    for (int i = 0; i < p->pages->num; i++) {
+        p->batch_task->addr[i] = (ram_addr_t)(rb->host + p->pages->offset[i]);
+    }
+
+    buffer_is_zero_dsa_batch_async(p->batch_task,
+                                   (const void **)p->batch_task->addr,
+                                   p->pages->num,
+                                   p->page_size);
+
+    int i = 0;
+    int j = pages->num - 1;
+
     /*
      * Sort the page offset array by moving all normal pages to
      * the left and all zero pages to the right of the array.
@@ -63,11 +121,12 @@ void multifd_send_zero_page_detect(MultiFDSendParams *p)
     while (i <= j) {
         uint64_t offset = pages->offset[i];
 
-        if (!buffer_is_zero(rb->host + offset, p->page_size)) {
+        if (!results[i]) {
             i++;
             continue;
         }
 
+        swap_result(results, i, j);
         swap_page_offset(pages->offset, i, j);
         ram_release_page(rb->idstr, offset);
         j--;
@@ -76,6 +135,15 @@ void multifd_send_zero_page_detect(MultiFDSendParams *p)
     pages->normal_num = i;
 }
 
+#else
+
+static void zero_page_detect_dsa(MultiFDSendParams *p)
+{
+    exit(1);
+}
+
+#endif
+
 void multifd_recv_zero_page_process(MultiFDRecvParams *p)
 {
     for (int i = 0; i < p->zero_num; i++) {
@@ -87,3 +155,24 @@ void multifd_recv_zero_page_process(MultiFDRecvParams *p)
         }
     }
 }
+
+/**
+ * multifd_send_zero_page_detect: Perform zero page detection on all pages.
+ *
+ * @param p A pointer to the send params.
+ */
+void multifd_send_zero_page_detect(MultiFDSendParams *p)
+{
+    MultiFDPages_t *pages = p->pages;
+
+    if (!multifd_zero_page_enabled()) {
+        pages->normal_num = pages->num;
+        return;
+    }
+
+    if (dsa_is_running()) {
+        zero_page_detect_dsa(p);
+    } else {
+        zero_page_detect_cpu(p);
+    }
+}
diff --git a/migration/multifd.c b/migration/multifd.c
index cfd3a92f6c..7316643d0a 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -818,6 +818,8 @@ void multifd_send_shutdown(void)
 
     multifd_send_terminate_threads();
 
+    dsa_cleanup();
+
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
         Error *local_err = NULL;
@@ -1155,11 +1157,20 @@ bool multifd_send_setup(void)
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     bool use_packets = multifd_use_packets();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
 
     if (!migrate_multifd()) {
         return true;
     }
 
+    if (dsa_init(dsa_parameter)) {
+        error_setg(&local_err, "multifd: Sender failed to initialize DSA.");
+        error_report_err(local_err);
+        return false;
+    }
+
+    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);
@@ -1393,6 +1404,7 @@ void multifd_recv_cleanup(void)
             qemu_thread_join(&p->thread);
         }
     }
+    dsa_cleanup();
     for (i = 0; i < migrate_multifd_channels(); i++) {
         multifd_recv_cleanup_channel(&multifd_recv_state->params[i]);
     }
@@ -1568,6 +1580,9 @@ int multifd_recv_setup(Error **errp)
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     bool use_packets = multifd_use_packets();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
+    int ret;
+    Error *local_err = NULL;
 
     /*
      * Return successfully if multiFD recv state is already initialised
@@ -1577,6 +1592,15 @@ int multifd_recv_setup(Error **errp)
         return 0;
     }
 
+    ret = dsa_init(dsa_parameter);
+    if (ret != 0) {
+        error_setg(&local_err, "multifd: Receiver failed to initialize DSA.");
+        error_propagate(errp, local_err);
+        return ret;
+    }
+
+    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);
@@ -1616,13 +1640,12 @@ int multifd_recv_setup(Error **errp)
 
     for (i = 0; i < thread_count; i++) {
         MultiFDRecvParams *p = &multifd_recv_state->params[i];
-        int ret;
-
         ret = multifd_recv_state->ops->recv_setup(p, errp);
         if (ret) {
             return ret;
         }
     }
+
     return 0;
 }
 
diff --git a/migration/multifd.h b/migration/multifd.h
index 16e27db5e9..b3717fae24 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -14,6 +14,7 @@
 #define QEMU_MIGRATION_MULTIFD_H
 
 #include "ram.h"
+#include "qemu/dsa.h"
 
 typedef struct MultiFDRecvData MultiFDRecvData;
 
-- 
2.30.2