From 7dda5dc82a776a39a7996020c188eb2a29187117 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 9 Apr 2013 17:43:43 +0200 Subject: [PATCH] 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 Signed-off-by: Paolo Bonzini Reviewed-by: Markus Armbruster Message-id: 1365522223-20153-1-git-send-email-pbonzini@redhat.com Signed-off-by: Anthony Liguori --- util/oslib-posix.c | 35 ++++++++++++++++++----------------- 1 file 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 -#if defined(CONFIG_VALGRIND) -static int running_on_valgrind = -1; -#else -# define running_on_valgrind 0 -#endif #ifdef CONFIG_LINUX #include #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; }