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authorPaolo Bonzini <pbonzini@redhat.com>2013-04-09 17:43:43 +0200
committerAnthony Liguori <aliguori@us.ibm.com>2013-04-16 16:10:20 -0500
commit7dda5dc82a776a39a7996020c188eb2a29187117 (patch)
treed121e12b3639341ba18cef1e3d6f3d13e5fbd5b7 /util
parent86c7dba0d0ed1e9e202f77f7414ce0faf2395a90 (diff)
migration: initialize RAM to zero
Using qemu_memalign only leaves the RAM zero by chance, because libc will usually use mmap to satisfy our huge requests. But memory will not be zero when using MALLOC_PERTURB_ with a nonzero value. In the case of incoming migration, this breaks a recently-introduced invariant (commit f1c7279, migration: do not sent zero pages in bulk stage, 2013-03-26). To fix this, use mmap ourselves to get a well-aligned, always zero block for the RAM. Mmap-ed memory is easy to "trim" at the sides. This also removes the need to do something special on valgrind (see commit c2a8238a, Support running QEMU on Valgrind, 2011-10-31), thus effectively reverts that patch. Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Message-id: 1365522223-20153-1-git-send-email-pbonzini@redhat.com Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'util')
-rw-r--r--util/oslib-posix.c35
1 files changed, 18 insertions, 17 deletions
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 4e4b8196be..3efc76320a 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -40,7 +40,6 @@ extern int daemon(int, int);
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)
-# define CONFIG_VALGRIND
#elif defined(__linux__) && defined(__s390x__)
/* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
# define QEMU_VMALLOC_ALIGN (256 * 4096)
@@ -52,12 +51,8 @@ extern int daemon(int, int);
#include "sysemu/sysemu.h"
#include "trace.h"
#include "qemu/sockets.h"
+#include <sys/mman.h>
-#if defined(CONFIG_VALGRIND)
-static int running_on_valgrind = -1;
-#else
-# define running_on_valgrind 0
-#endif
#ifdef CONFIG_LINUX
#include <sys/syscall.h>
#endif
@@ -108,22 +103,28 @@ void *qemu_memalign(size_t alignment, size_t size)
/* alloc shared memory pages */
void *qemu_vmalloc(size_t size)
{
- void *ptr;
size_t align = QEMU_VMALLOC_ALIGN;
+ size_t total = size + align - getpagesize();
+ void *ptr = mmap(0, total, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+ size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
-#if defined(CONFIG_VALGRIND)
- if (running_on_valgrind < 0) {
- /* First call, test whether we are running on Valgrind.
- This is a substitute for RUNNING_ON_VALGRIND from valgrind.h. */
- const char *ld = getenv("LD_PRELOAD");
- running_on_valgrind = (ld != NULL && strstr(ld, "vgpreload"));
+ if (ptr == MAP_FAILED) {
+ fprintf(stderr, "Failed to allocate %zu B: %s\n",
+ size, strerror(errno));
+ abort();
}
-#endif
- if (size < align || running_on_valgrind) {
- align = getpagesize();
+ ptr += offset;
+ total -= offset;
+
+ if (offset > 0) {
+ munmap(ptr - offset, offset);
}
- ptr = qemu_memalign(align, size);
+ if (total > size) {
+ munmap(ptr + size, total - size);
+ }
+
trace_qemu_vmalloc(size, ptr);
return ptr;
}