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authorMichael S. Tsirkin <mst@redhat.com>2015-12-02 21:14:12 +0200
committerMichael S. Tsirkin <mst@redhat.com>2015-12-02 22:38:23 +0200
commit7197fb4058bcb68986bae2bb2c04d6370f3e7218 (patch)
treec61e664c27278f8497fb9fec90cbb88383bf1d0e
parent0560b0e97df3da43651158c799c6d889f27529c3 (diff)
downloadqemu-7197fb4058bcb68986bae2bb2c04d6370f3e7218.tar.gz
qemu-7197fb4058bcb68986bae2bb2c04d6370f3e7218.tar.xz
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util/mmap-alloc: fix hugetlb support on ppc64
Since commit 8561c9244ddf1122d "exec: allocate PROT_NONE pages on top of RAM", it is no longer possible to back guest RAM with hugepages on ppc64 hosts: mmap(NULL, 285212672, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x3fff57000000 mmap(0x3fff57000000, 268435456, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 19, 0) = -1 EBUSY (Device or resource busy) This is because on ppc64, Linux fixes a page size for a virtual address at mmap time, so we can't switch a range of memory from anonymous small pages to hugetlbs with MAP_FIXED. See commit d0f13e3c20b6fb73ccb467bdca97fa7cf5a574cd ("[POWERPC] Introduce address space "slices"") in Linux history for the details. Detect this and create the PROT_NONE mapping using the same fd. Naturally, this makes the guard page bigger with hugetlbfs. Based on patch by Greg Kurz. Acked-by: Rik van Riel <riel@redhat.com> Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com> Tested-by: Greg Kurz <gkurz@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--include/qemu/mmap-alloc.h2
-rw-r--r--util/mmap-alloc.c39
-rw-r--r--util/oslib-posix.c24
3 files changed, 42 insertions, 23 deletions
diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
index 56388e689..0899b2f01 100644
--- a/include/qemu/mmap-alloc.h
+++ b/include/qemu/mmap-alloc.h
@@ -3,6 +3,8 @@
#include "qemu-common.h"
+size_t qemu_fd_getpagesize(int fd);
+
void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared);
void qemu_ram_munmap(void *ptr, size_t size);
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index c37acbe58..54793a5dc 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -14,6 +14,32 @@
#include <sys/mman.h>
#include <assert.h>
+#define HUGETLBFS_MAGIC 0x958458f6
+
+#ifdef CONFIG_LINUX
+#include <sys/vfs.h>
+#endif
+
+size_t qemu_fd_getpagesize(int fd)
+{
+#ifdef CONFIG_LINUX
+ struct statfs fs;
+ int ret;
+
+ if (fd != -1) {
+ do {
+ ret = fstatfs(fd, &fs);
+ } while (ret != 0 && errno == EINTR);
+
+ if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
+ return fs.f_bsize;
+ }
+ }
+#endif
+
+ return getpagesize();
+}
+
void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
{
/*
@@ -21,7 +47,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
* space, even if size is already aligned.
*/
size_t total = size + align;
+#if defined(__powerpc64__) && defined(__linux__)
+ /* On ppc64 mappings in the same segment (aka slice) must share the same
+ * page size. Since we will be re-allocating part of this segment
+ * from the supplied fd, we should make sure to use the same page size,
+ * unless we are using the system page size, in which case anonymous memory
+ * is OK. Use align as a hint for the page size.
+ * In this case, set MAP_NORESERVE to avoid allocating backing store memory.
+ */
+ int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
+ int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
+ void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
+#else
void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+#endif
size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
void *ptr1;
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 914cef5c2..d25f6715c 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -46,7 +46,6 @@ extern int daemon(int, int);
#else
# define QEMU_VMALLOC_ALIGN getpagesize()
#endif
-#define HUGETLBFS_MAGIC 0x958458f6
#include <termios.h>
#include <unistd.h>
@@ -65,7 +64,6 @@ extern int daemon(int, int);
#ifdef CONFIG_LINUX
#include <sys/syscall.h>
-#include <sys/vfs.h>
#endif
#ifdef __FreeBSD__
@@ -340,26 +338,6 @@ static void sigbus_handler(int signal)
siglongjmp(sigjump, 1);
}
-static size_t fd_getpagesize(int fd)
-{
-#ifdef CONFIG_LINUX
- struct statfs fs;
- int ret;
-
- if (fd != -1) {
- do {
- ret = fstatfs(fd, &fs);
- } while (ret != 0 && errno == EINTR);
-
- if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
- return fs.f_bsize;
- }
- }
-#endif
-
- return getpagesize();
-}
-
void os_mem_prealloc(int fd, char *area, size_t memory)
{
int ret;
@@ -387,7 +365,7 @@ void os_mem_prealloc(int fd, char *area, size_t memory)
exit(1);
} else {
int i;
- size_t hpagesize = fd_getpagesize(fd);
+ size_t hpagesize = qemu_fd_getpagesize(fd);
size_t numpages = DIV_ROUND_UP(memory, hpagesize);
/* MAP_POPULATE silently ignores failures */