[1/2] migration: Receiving a zero page non zero is an error

Commit Message

Juan Quintela Oct. 19, 2023, 8:52 a.m. UTC

We don't allow non zero compressed pages since:

commit 3edcd7e6ebae3ef0ac178eed5f4225803159562d
Author: Peter Lieven <[e-mail]>
Date:   Tue Mar 26 10:58:35 2013 +0100

    migration: search for zero instead of dup pages

RDMA case is a bit more complicated, but they don't handle it since:

commit a1febc4950f2c6232c002f401d7cd409f6fa6a88
Author: Richard Henderson <[e-mail]>
Date:   Mon Aug 29 11:46:14 2016 -0700

    cutils: Export only buffer_is_zero

Signed-off-by: Juan Quintela <[e-mail]>
---
 migration/ram.c  | 15 +++++++++++----
 migration/rdma.c |  6 +++++-
 2 files changed, 16 insertions(+), 5 deletions(-)

Comments

Fabiano Rosas Oct. 19, 2023, 9:22 p.m. UTC | #1

Juan Quintela <[e-mail]> writes:

> We don't allow non zero compressed pages since:
>
> commit 3edcd7e6ebae3ef0ac178eed5f4225803159562d
> Author: Peter Lieven <[e-mail]>
> Date:   Tue Mar 26 10:58:35 2013 +0100
>
>     migration: search for zero instead of dup pages
>
> RDMA case is a bit more complicated, but they don't handle it since:
>
> commit a1febc4950f2c6232c002f401d7cd409f6fa6a88
> Author: Richard Henderson <[e-mail]>
> Date:   Mon Aug 29 11:46:14 2016 -0700
>
>     cutils: Export only buffer_is_zero
>
> Signed-off-by: Juan Quintela <[e-mail]>

Reviewed-by: Fabiano Rosas <[e-mail]>

Patch

diff --git a/migration/ram.c b/migration/ram.c
index c844151ee9..0dd8bbb339 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3730,16 +3730,18 @@  int ram_load_postcopy(QEMUFile *f, int channel)
         switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
         case RAM_SAVE_FLAG_ZERO:
             ch = qemu_get_byte(f);
+            if (ch != 0) {
+                error_report("Found a zero page with value %d", ch);
+                ret = -EINVAL;
+                break;
+            }
             /*
              * Can skip to set page_buffer when
              * this is a zero page and (block->page_size == TARGET_PAGE_SIZE).
              */
-            if (ch || !matches_target_page_size) {
+            if (!matches_target_page_size) {
                 memset(page_buffer, ch, TARGET_PAGE_SIZE);
             }
-            if (ch) {
-                tmp_page->all_zero = false;
-            }
             break;
 
         case RAM_SAVE_FLAG_PAGE:
@@ -4044,6 +4046,11 @@  static int ram_load_precopy(QEMUFile *f)
 
         case RAM_SAVE_FLAG_ZERO:
             ch = qemu_get_byte(f);
+            if (ch != 0) {
+                error_report("Found a zero page with value %d", ch);
+                ret = -EINVAL;
+                break;
+            }
             ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
             break;
 
diff --git a/migration/rdma.c b/migration/rdma.c
index 2a1852ec7f..2d963fd147 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -3592,7 +3592,11 @@  int rdma_registration_handle(QEMUFile *f)
 
             host_addr = block->local_host_addr +
                             (comp->offset - block->offset);
-
+            if (comp->value) {
+                error_report("rdma: Zero page with non-zero (%d) value",
+                             comp->value);
+                goto err;
+            }
             ram_handle_compressed(host_addr, comp->value, comp->length);
             break;