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[Qemu-devel] [PULL 9/9] util/mmap-alloc: fix hugetlb support on ppc64
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PULL 9/9] util/mmap-alloc: fix hugetlb support on ppc64 |
Date: |
Wed, 2 Dec 2015 22:35:50 +0200 |
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.
Cc: Rik van Riel <address@hidden>
Reviewed-by: Greg Kurz <address@hidden>
Tested-by: Greg Kurz <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
include/qemu/mmap-alloc.h | 2 ++
util/mmap-alloc.c | 39 +++++++++++++++++++++++++++++++++++++++
util/oslib-posix.c | 24 +-----------------------
3 files changed, 42 insertions(+), 23 deletions(-)
diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
index 56388e6..0899b2f 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 c37acbe..54793a5 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 914cef5..d25f671 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 */
--
MST
- [Qemu-devel] [PULL 0/9] virtio,vhost,mmap fixes for 2.5, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 1/9] vhost-user-test: fix chardriver race, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 2/9] vhost-user-test: use unix port for migration, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 3/9] vhost-user-test: fix crash with glib < 2.36, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 4/9] vhost-user: verify that number of queues is non-zero, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 6/9] tests/vhost-user-bridge.c: fix fd leakage, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 5/9] vhost: drop dead code, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 7/9] virtio: handle non-virtio-1-capable backend for ccw, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 8/9] virtio-pci: Set the QEMU_PCI_CAP_EXPRESS capability early in its DeviceClass realize method, Michael S. Tsirkin, 2015/12/02
- [Qemu-devel] [PULL 9/9] util/mmap-alloc: fix hugetlb support on ppc64,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PULL 0/9] virtio,vhost,mmap fixes for 2.5, Michael S. Tsirkin, 2015/12/02