exec.c: Ensure right alignment also for file backed ram

While in the anonymous ram case we already take care of the right alignment
such an alignment gurantee does not exist for file backed ram allocation.

Instead, pagesize is used for alignment. On s390 this is not enough for gmap,
as we need to satisfy an alignment up to segments.
Reported-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>

Message-Id: <1461585338-45863-1-git-send-email-dingel@linux.vnet.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit d2f39add)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

exec.c

@@ -1296,7 +1296,7 @@ static void *file_ram_alloc(RAMBlock *block,
     }
 
     page_size = qemu_fd_getpagesize(fd);
-    block->mr->align = page_size;
+    block->mr->align = MAX(page_size, QEMU_VMALLOC_ALIGN);
 
     if (memory < page_size) {
         error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
@@ -1317,7 +1317,8 @@ static void *file_ram_alloc(RAMBlock *block,
         perror("ftruncate");
     }
 
-    area = qemu_ram_mmap(fd, memory, page_size, block->flags & RAM_SHARED);
+    area = qemu_ram_mmap(fd, memory, block->mr->align,
+                         block->flags & RAM_SHARED);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");

include/qemu/osdep.h

@@ -247,6 +247,19 @@ void qemu_anon_ram_free(void *ptr, size_t size);
 
 #endif
 
+#if defined(__linux__) && \
+    (defined(__x86_64__) || defined(__arm__) || defined(__aarch64__))
+   /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
+      Valgrind does not support alignments larger than 1 MiB,
+      therefore we need special code which handles running on Valgrind. */
+#  define QEMU_VMALLOC_ALIGN (512 * 4096)
+#elif defined(__linux__) && defined(__s390x__)
+   /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
+#  define QEMU_VMALLOC_ALIGN (256 * 4096)
+#else
+#  define QEMU_VMALLOC_ALIGN getpagesize()
+#endif
+
 int qemu_madvise(void *addr, size_t len, int advice);
 
 int qemu_open(const char *name, int flags, ...);

util/oslib-posix.c

@@ -26,19 +26,6 @@
  * THE SOFTWARE.
  */
 
-#if defined(__linux__) && \
-    (defined(__x86_64__) || defined(__arm__) || defined(__aarch64__))
-   /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
-      Valgrind does not support alignments larger than 1 MiB,
-      therefore we need special code which handles running on Valgrind. */
-#  define QEMU_VMALLOC_ALIGN (512 * 4096)
-#elif defined(__linux__) && defined(__s390x__)
-   /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
-#  define QEMU_VMALLOC_ALIGN (256 * 4096)
-#else
-#  define QEMU_VMALLOC_ALIGN getpagesize()
-#endif
-
 #include "qemu/osdep.h"
 #include <termios.h>
 #include <termios.h>