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author | Paolo Bonzini <pbonzini@redhat.com> | 2013-04-09 17:43:43 +0200 |
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committer | Anthony Liguori <aliguori@us.ibm.com> | 2013-04-16 16:10:20 -0500 |
commit | 7dda5dc82a776a39a7996020c188eb2a29187117 (patch) | |
tree | d121e12b3639341ba18cef1e3d6f3d13e5fbd5b7 | |
parent | 86c7dba0d0ed1e9e202f77f7414ce0faf2395a90 (diff) | |
download | qemu-7dda5dc82a776a39a7996020c188eb2a29187117.zip qemu-7dda5dc82a776a39a7996020c188eb2a29187117.tar.gz qemu-7dda5dc82a776a39a7996020c188eb2a29187117.tar.bz2 |
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>
-rw-r--r-- | util/oslib-posix.c | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/util/oslib-posix.c b/util/oslib-posix.c index 4e4b819..3efc763 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; } |