[PATCH v6 11/16] PoC: libs/guest: use foreign copy during migration

[Frediano Ziglio <freddy77@gmail.com>]

From: Edwin Török <edwin.torok@citrix.com>

ministat confirms the improvement:

```
x baseline
+ foreigncopy
    N           Min           Max        Median           Avg        Stddev
x  20     1.1306997     1.1447931     1.1356569     1.1365742   0.003242175
+  20     0.4311504    0.44180303    0.43616705    0.43600089  0.0031094689
Difference at 95.0% confidence
	-0.700573 +/- 0.00203311
	-61.639% +/- 0.133355%
	(Student's t, pooled s = 0.00317652)
```

The tests pass too, which means that it has correctly migrated all guest
memory.

Frediano: This PoC was adapted to be included in a final series.

Signed-off-by: Edwin Török <edwin.torok@citrix.com>
Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/libs/guest/xg_sr_common.h  |  1 +
 tools/libs/guest/xg_sr_restore.c | 43 +++--------------
 tools/libs/guest/xg_sr_save.c    | 82 +++++++++-----------------------
 3 files changed, 31 insertions(+), 95 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index e37f805240..d8d8a0f9f7 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -256,6 +256,7 @@ struct xc_sr_context
             unsigned long nr_deferred_pages;
             xc_hypercall_buffer_t dirty_bitmap_hbuf;
             struct xc_sr_context_save_buffers *buffers;
+            void *dest_buf;
         } save;
 
         struct /* Restore data. */
diff --git a/tools/libs/guest/xg_sr_restore.c b/tools/libs/guest/xg_sr_restore.c
index fb46142d87..ff27560ff7 100644
--- a/tools/libs/guest/xg_sr_restore.c
+++ b/tools/libs/guest/xg_sr_restore.c
@@ -259,8 +259,8 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
     xen_pfn_t *mfns = malloc(count * sizeof(*mfns));
     int *map_errs = malloc(count * sizeof(*map_errs));
     int rc;
-    void *mapping = NULL, *guest_page = NULL;
     unsigned nr_pages;
+    void *const source = page_data;
 
     if ( !mfns || !map_errs )
     {
@@ -295,27 +295,8 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
     if ( nr_pages == 0 )
         goto done;
 
-    mapping = guest_page = xenforeignmemory_map(
-        xch->fmem, ctx->domid, PROT_READ | PROT_WRITE,
-        nr_pages, mfns, map_errs);
-    if ( !mapping )
-    {
-        rc = -1;
-        PERROR("Unable to map %u mfns for %u pages of data",
-               nr_pages, count);
-        goto err;
-    }
-
     for ( unsigned i = 0; i < nr_pages; ++i )
     {
-        if ( map_errs[i] )
-        {
-            rc = -1;
-            ERROR("Mapping pfn %#"PRIpfn" (mfn %#"PRIpfn", type %#"PRIx32") failed with %d",
-                  pfns[i], mfns[i], types[i], map_errs[i]);
-            goto err;
-        }
-
         /* Undo page normalisation done by the saver. */
         rc = ctx->restore.ops.localise_page(ctx, types[i], page_data);
         if ( rc )
@@ -325,29 +306,19 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
             goto err;
         }
 
-        if ( ctx->restore.verify )
-        {
-            /* Verify mode - compare incoming data to what we already have. */
-            if ( memcmp(guest_page, page_data, PAGE_SIZE) )
-                ERROR("verify pfn %#"PRIpfn" failed (type %#"PRIx32")",
-                      pfns[i], types[i] >> XEN_DOMCTL_PFINFO_LTAB_SHIFT);
-        }
-        else
-        {
-            /* Regular mode - copy incoming data into place. */
-            memcpy(guest_page, page_data, PAGE_SIZE);
-        }
-
-        guest_page += PAGE_SIZE;
         page_data += PAGE_SIZE;
     }
+    if ( !ctx->restore.verify )
+    {
+        rc = xg_foreignmemory_copy_to(xch, ctx->domid, nr_pages, mfns, source);
+        if ( rc < 0 )
+            goto err;
+    }
 
  done:
     rc = 0;
 
  err:
-    if ( mapping )
-        xenforeignmemory_unmap(xch->fmem, mapping, nr_pages);
 
     free(map_errs);
     free(mfns);
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 8a22267fdf..7a48f6b0a3 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -87,12 +87,10 @@ static int write_batch(struct xc_sr_context *ctx)
 {
     xc_interface *xch = ctx->xch;
     xen_pfn_t *mfns, *types;
-    void *guest_mapping = NULL;
     void **local_pages;
     int *errors, rc = -1;
-    unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
+    unsigned int i, nr_pages = 0;
     unsigned int nr_pfns = ctx->save.nr_batch_pfns;
-    void *page, *orig_page;
     uint64_t *rec_pfns;
     struct iovec *iov; int iovcnt = 0;
     struct {
@@ -167,62 +165,18 @@ static int write_batch(struct xc_sr_context *ctx)
 
     iovcnt = 2;
 
-    if ( nr_pages > 0 )
+    rc = xg_foreignmemory_copy_from(xch, ctx->domid, nr_pages, ctx->save.dest_buf, mfns);
+    if ( rc < 0 )
     {
-        guest_mapping = xenforeignmemory_map(
-            xch->fmem, ctx->domid, PROT_READ, nr_pages, mfns, errors);
-        if ( !guest_mapping )
-        {
-            PERROR("Failed to map guest pages");
-            goto err;
-        }
-        nr_pages_mapped = nr_pages;
-
-        for ( i = 0, p = 0; i < nr_pfns; ++i )
-        {
-            if ( !page_type_has_stream_data(types[i]) )
-                continue;
-
-            if ( errors[p] )
-            {
-                ERROR("Mapping of pfn %#"PRIpfn" (mfn %#"PRIpfn") failed %d",
-                      ctx->save.batch_pfns[i], mfns[p], errors[p]);
-                goto err;
-            }
-
-            orig_page = page = guest_mapping + (p * PAGE_SIZE);
-            rc = ctx->save.ops.normalise_page(ctx, types[i], &page);
-
-            if ( orig_page != page )
-                local_pages[i] = page;
-
-            if ( rc )
-            {
-                if ( rc == -1 && errno == EAGAIN )
-                {
-                    set_bit(ctx->save.batch_pfns[i], ctx->save.deferred_pages);
-                    ++ctx->save.nr_deferred_pages;
-                    types[i] = XEN_DOMCTL_PFINFO_XTAB;
-                    --nr_pages;
-                }
-                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
-            {
-                iov[iovcnt - 1].iov_len += PAGE_SIZE;
-            }
+        ERROR("xg_foreignmemory_copy_from failed");
+        goto err;
+    }
 
-            rc = -1;
-            ++p;
-        }
+    if ( nr_pages )
+    {
+        iov[iovcnt].iov_base = ctx->save.dest_buf;
+        iov[iovcnt].iov_len = nr_pages << XC_PAGE_SHIFT;
+        iovcnt++;
     }
 
     hdrs.rec.length += nr_pages * PAGE_SIZE;
@@ -239,8 +193,6 @@ static int write_batch(struct xc_sr_context *ctx)
     rc = ctx->save.nr_batch_pfns = 0;
 
  err:
-    if ( guest_mapping )
-        xenforeignmemory_unmap(xch->fmem, guest_mapping, nr_pages_mapped);
     for ( i = 0; local_pages && i < nr_pfns; ++i )
     {
         free(local_pages[i]);
@@ -765,6 +717,7 @@ static int setup(struct xc_sr_context *ctx)
 {
     xc_interface *xch = ctx->xch;
     int rc;
+    const unsigned dest_buf_len = MAX_BATCH_SIZE * XC_PAGE_SIZE;
     DECLARE_HYPERCALL_BUFFER_SHADOW(unsigned long, dirty_bitmap,
                                     &ctx->save.dirty_bitmap_hbuf);
 
@@ -776,6 +729,16 @@ static int setup(struct xc_sr_context *ctx)
         xch, dirty_bitmap, NRPAGES(bitmap_size(ctx->save.p2m_size)));
     ctx->save.deferred_pages = bitmap_alloc(ctx->save.p2m_size);
     ctx->save.buffers = calloc(1, sizeof(*ctx->save.buffers));
+    ctx->save.dest_buf = NULL;
+
+    rc = posix_memalign(&ctx->save.dest_buf, XC_PAGE_SIZE, dest_buf_len);
+    if ( rc )
+    {
+        ERROR("Unable to allocate %u bytes of buffer", dest_buf_len);
+        errno = rc;
+        rc = -1;
+        goto err;
+    }
 
     if ( !dirty_bitmap || !ctx->save.deferred_pages || !ctx->save.buffers)
     {
@@ -810,6 +773,7 @@ static void cleanup(struct xc_sr_context *ctx)
                                    NRPAGES(bitmap_size(ctx->save.p2m_size)));
     free(ctx->save.deferred_pages);
     free(ctx->save.buffers);
+    free(ctx->save.dest_buf);
 }
 
 /*
-- 
2.43.0