File libxc-sr-save-guest_data.patch of Package xen.34726

From: Olaf Hering <olaf@aepfle.de>
Date: Fri, 23 Oct 2020 11:40:45 +0200
Subject: libxc sr save guest_data

tools/guest: save: move guest_data array

Remove allocation from hotpath, move guest_data array into preallocated space.

Because this was allocated with calloc:
Adjust the loop to clear unused entries as needed.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 tools/libxc/xc_sr_common.h |  2 ++
 tools/libxc/xc_sr_save.c   | 11 ++++++-----
 2 files changed, 8 insertions(+), 5 deletions(-)

--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_common.h
+++ xen-4.14.0-testing/tools/libxc/xc_sr_common.h
@@ -224,6 +224,8 @@ struct xc_sr_save_arrays {
     struct iovec iov[MAX_BATCH_SIZE + 4];
     /* write_batch */
     uint64_t rec_pfns[MAX_BATCH_SIZE];
+    /* write_batch: Pointers to page data to send. Mapped gfns or local allocations. */
+    void *guest_data[MAX_BATCH_SIZE];
 };
 
 struct xc_sr_restore_arrays {
--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_save.c
+++ xen-4.14.0-testing/tools/libxc/xc_sr_save.c
@@ -90,7 +90,7 @@ static int write_batch(struct xc_sr_cont
     xc_interface *xch = ctx->xch;
     xen_pfn_t *mfns = ctx->save.m->mfns, *types = ctx->save.m->types;
     void *guest_mapping = NULL;
-    void **guest_data = NULL;
+    void **guest_data = ctx->save.m->guest_data;
     void **local_pages = NULL;
     int *errors = ctx->save.m->errors, rc = -1;
     unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
@@ -105,12 +105,10 @@ static int write_batch(struct xc_sr_cont
 
     assert(nr_pfns != 0);
 
-    /* Pointers to page data to send.  Mapped gfns or local allocations. */
-    guest_data = calloc(nr_pfns, sizeof(*guest_data));
     /* Pointers to locally allocated pages.  Need freeing. */
     local_pages = calloc(nr_pfns, sizeof(*local_pages));
 
-    if ( !guest_data || !local_pages )
+    if ( !local_pages )
     {
         ERROR("Unable to allocate arrays for a batch of %u pages",
               nr_pfns);
@@ -166,7 +164,10 @@ static int write_batch(struct xc_sr_cont
         for ( i = 0, p = 0; i < nr_pfns; ++i )
         {
             if ( page_type_has_stream_data(types[i]) == false )
+            {
+                guest_data[i] = NULL;
                 continue;
+            }
 
             if ( errors[p] )
             {
@@ -183,6 +184,7 @@ static int write_batch(struct xc_sr_cont
 
             if ( rc )
             {
+                guest_data[i] = NULL;
                 if ( rc == -1 && errno == EAGAIN )
                 {
                     set_bit(ctx->save.m->batch_pfns[i], ctx->save.deferred_pages);
@@ -256,7 +258,6 @@ static int write_batch(struct xc_sr_cont
     for ( i = 0; local_pages && i < nr_pfns; ++i )
         free(local_pages[i]);
     free(local_pages);
-    free(guest_data);
 
     return rc;
 }