[PATCH v3 8/9] libs/guest: fill directly iov structure

[Frediano Ziglio <freddy77@xxxxxxxxx>]

From: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>

Instead of storing page pointers into an array and lately adding to
iov vector add the pages directly to iov to avoid "guest_data"
array.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
---
 tools/libs/guest/xg_sr_common.h |  1 -
 tools/libs/guest/xg_sr_save.c   | 62 ++++++++++++---------------------
 2 files changed, 22 insertions(+), 41 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index 77312bae9cf5..797b4d1a7da1 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -215,7 +215,6 @@ struct xc_sr_context_save_buffers
     xen_pfn_t mfns[MAX_BATCH_SIZE];
     xen_pfn_t types[MAX_BATCH_SIZE];
     int errors[MAX_BATCH_SIZE];
-    void *guest_data[MAX_BATCH_SIZE];
     void *local_pages[MAX_BATCH_SIZE];
     struct iovec iov[MAX_BATCH_SIZE + 2]; /* headers + data */
     uint64_t rec_pfns[MAX_BATCH_SIZE];
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 7d8055a3f9e8..593268f176a6 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -88,7 +88,6 @@ static int write_batch(struct xc_sr_context *ctx)
     xc_interface *xch = ctx->xch;
     xen_pfn_t *mfns, *types;
     void *guest_mapping = NULL;
-    void **guest_data;
     void **local_pages;
     int *errors, rc = -1;
     unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
@@ -114,9 +113,6 @@ static int write_batch(struct xc_sr_context *ctx)
     types = ctx->save.buffers->types;
     /* Errors from attempting to map the gfns. */
     errors = ctx->save.buffers->errors;
-    /* Pointers to page data to send.  Mapped gfns or local allocations. */
-    guest_data = ctx->save.buffers->guest_data;
-    memset(guest_data, 0, sizeof(*guest_data) * nr_pfns);
     /* Pointers to locally allocated pages.  Need freeing. */
     local_pages = ctx->save.buffers->local_pages;
     memset(local_pages, 0, sizeof(*local_pages) * nr_pfns);
@@ -159,6 +155,19 @@ static int write_batch(struct xc_sr_context *ctx)
         mfns[nr_pages++] = mfns[i];
     }
 
+    hdrs.rec.length = sizeof(hdrs.page_data);
+    hdrs.rec.length += nr_pfns * sizeof(*rec_pfns);
+
+    hdrs.page_data.count = nr_pfns;
+
+    iov[0].iov_base = &hdrs;
+    iov[0].iov_len = sizeof(hdrs);
+
+    iov[1].iov_base = rec_pfns;
+    iov[1].iov_len = nr_pfns * sizeof(*rec_pfns);
+
+    iovcnt = 2;
+
     if ( nr_pages > 0 )
     {
         guest_mapping = xenforeignmemory_map(
@@ -200,60 +209,33 @@ static int write_batch(struct xc_sr_context *ctx)
                 else
                     goto err;
             }
+            else if ( iov[iovcnt-1].iov_base + iov[iovcnt-1].iov_len != page )
+            {
+                iov[iovcnt].iov_base = page;
+                iov[iovcnt].iov_len = PAGE_SIZE;
+                iovcnt++;
+            }
             else
-                guest_data[i] = page;
+            {
+                iov[iovcnt-1].iov_len += PAGE_SIZE;
+            }
 
             rc = -1;
             ++p;
         }
     }
 
-    hdrs.rec.length = sizeof(hdrs.page_data);
-    hdrs.rec.length += nr_pfns * sizeof(*rec_pfns);
     hdrs.rec.length += nr_pages * PAGE_SIZE;
 
-    hdrs.page_data.count = nr_pfns;
-
     for ( i = 0; i < nr_pfns; ++i )
         rec_pfns[i] = ((uint64_t)(types[i]) << 32) | ctx->save.batch_pfns[i];
 
-    iov[0].iov_base = &hdrs;
-    iov[0].iov_len = sizeof(hdrs);
-
-    iov[1].iov_base = rec_pfns;
-    iov[1].iov_len = nr_pfns * sizeof(*rec_pfns);
-
-    iovcnt = 2;
-
-    if ( nr_pages )
-    {
-        for ( i = 0; i < nr_pfns; ++i )
-        {
-            if ( !guest_data[i] )
-                continue;
-
-            if ( iov[iovcnt-1].iov_base + iov[iovcnt-1].iov_len != 
guest_data[i] )
-            {
-                iov[iovcnt].iov_base = guest_data[i];
-                iov[iovcnt].iov_len = PAGE_SIZE;
-                iovcnt++;
-            }
-            else
-            {
-                iov[iovcnt-1].iov_len += PAGE_SIZE;
-            }
-            --nr_pages;
-        }
-    }
-
     if ( writev_exact(ctx->fd, iov, iovcnt) )
     {
         PERROR("Failed to write page data to stream");
         goto err;
     }
 
-    /* Sanity check we have sent all the pages we expected to. */
-    assert(nr_pages == 0);
     rc = ctx->save.nr_batch_pfns = 0;
 
  err:
-- 
2.54.0