mirror of
https://gitlab.com/qemu-project/qemu
synced 2024-09-06 18:05:37 +00:00
![Peter Xu](/assets/img/avatar_default.png)
This new helper fetches file system type for a fd. Only Linux is implemented so far. Currently only tmpfs and hugetlbfs are defined, but it can grow as needed. Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
304 lines
8.9 KiB
C
304 lines
8.9 KiB
C
/*
|
|
* Support for RAM backed by mmaped host memory.
|
|
*
|
|
* Copyright (c) 2015 Red Hat, Inc.
|
|
*
|
|
* Authors:
|
|
* Michael S. Tsirkin <mst@redhat.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2 or
|
|
* later. See the COPYING file in the top-level directory.
|
|
*/
|
|
|
|
#ifdef CONFIG_LINUX
|
|
#include <linux/mman.h>
|
|
#else /* !CONFIG_LINUX */
|
|
#define MAP_SYNC 0x0
|
|
#define MAP_SHARED_VALIDATE 0x0
|
|
#endif /* CONFIG_LINUX */
|
|
|
|
#include "qemu/osdep.h"
|
|
#include "qemu/mmap-alloc.h"
|
|
#include "qemu/host-utils.h"
|
|
#include "qemu/cutils.h"
|
|
#include "qemu/error-report.h"
|
|
|
|
#define HUGETLBFS_MAGIC 0x958458f6
|
|
|
|
#ifdef CONFIG_LINUX
|
|
#include <sys/vfs.h>
|
|
#include <linux/magic.h>
|
|
#endif
|
|
|
|
QemuFsType qemu_fd_getfs(int fd)
|
|
{
|
|
#ifdef CONFIG_LINUX
|
|
struct statfs fs;
|
|
int ret;
|
|
|
|
if (fd < 0) {
|
|
return QEMU_FS_TYPE_UNKNOWN;
|
|
}
|
|
|
|
do {
|
|
ret = fstatfs(fd, &fs);
|
|
} while (ret != 0 && errno == EINTR);
|
|
|
|
switch (fs.f_type) {
|
|
case TMPFS_MAGIC:
|
|
return QEMU_FS_TYPE_TMPFS;
|
|
case HUGETLBFS_MAGIC:
|
|
return QEMU_FS_TYPE_HUGETLBFS;
|
|
default:
|
|
return QEMU_FS_TYPE_UNKNOWN;
|
|
}
|
|
#else
|
|
return QEMU_FS_TYPE_UNKNOWN;
|
|
#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;
|
|
}
|
|
}
|
|
#ifdef __sparc__
|
|
/* SPARC Linux needs greater alignment than the pagesize */
|
|
return QEMU_VMALLOC_ALIGN;
|
|
#endif
|
|
#endif
|
|
|
|
return qemu_real_host_page_size();
|
|
}
|
|
|
|
#define OVERCOMMIT_MEMORY_PATH "/proc/sys/vm/overcommit_memory"
|
|
static bool map_noreserve_effective(int fd, uint32_t qemu_map_flags)
|
|
{
|
|
#if defined(__linux__)
|
|
const bool readonly = qemu_map_flags & QEMU_MAP_READONLY;
|
|
const bool shared = qemu_map_flags & QEMU_MAP_SHARED;
|
|
gchar *content = NULL;
|
|
const char *endptr;
|
|
unsigned int tmp;
|
|
|
|
/*
|
|
* hugeltb accounting is different than ordinary swap reservation:
|
|
* a) Hugetlb pages from the pool are reserved for both private and
|
|
* shared mappings. For shared mappings, all mappers have to specify
|
|
* MAP_NORESERVE.
|
|
* b) MAP_NORESERVE is not affected by /proc/sys/vm/overcommit_memory.
|
|
*/
|
|
if (qemu_fd_getpagesize(fd) != qemu_real_host_page_size()) {
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Accountable mappings in the kernel that can be affected by MAP_NORESEVE
|
|
* are private writable mappings (see mm/mmap.c:accountable_mapping() in
|
|
* Linux). For all shared or readonly mappings, MAP_NORESERVE is always
|
|
* implicitly active -- no reservation; this includes shmem. The only
|
|
* exception is shared anonymous memory, it is accounted like private
|
|
* anonymous memory.
|
|
*/
|
|
if (readonly || (shared && fd >= 0)) {
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* MAP_NORESERVE is globally ignored for applicable !hugetlb mappings when
|
|
* memory overcommit is set to "never". Sparse memory regions aren't really
|
|
* possible in this system configuration.
|
|
*
|
|
* Bail out now instead of silently committing way more memory than
|
|
* currently desired by the user.
|
|
*/
|
|
if (g_file_get_contents(OVERCOMMIT_MEMORY_PATH, &content, NULL, NULL) &&
|
|
!qemu_strtoui(content, &endptr, 0, &tmp) &&
|
|
(!endptr || *endptr == '\n')) {
|
|
if (tmp == 2) {
|
|
error_report("Skipping reservation of swap space is not supported:"
|
|
" \"" OVERCOMMIT_MEMORY_PATH "\" is \"2\"");
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
/* this interface has been around since Linux 2.6 */
|
|
error_report("Skipping reservation of swap space is not supported:"
|
|
" Could not read: \"" OVERCOMMIT_MEMORY_PATH "\"");
|
|
return false;
|
|
#endif
|
|
/*
|
|
* E.g., FreeBSD used to define MAP_NORESERVE, never implemented it,
|
|
* and removed it a while ago.
|
|
*/
|
|
error_report("Skipping reservation of swap space is not supported");
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Reserve a new memory region of the requested size to be used for mapping
|
|
* from the given fd (if any).
|
|
*/
|
|
static void *mmap_reserve(size_t size, int fd)
|
|
{
|
|
int flags = MAP_PRIVATE;
|
|
|
|
#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, to
|
|
* this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
|
|
* avoid allocating backing store memory.
|
|
* We do this unless we are using the system page size, in which case
|
|
* anonymous memory is OK.
|
|
*/
|
|
if (fd == -1 || qemu_fd_getpagesize(fd) == qemu_real_host_page_size()) {
|
|
fd = -1;
|
|
flags |= MAP_ANONYMOUS;
|
|
} else {
|
|
flags |= MAP_NORESERVE;
|
|
}
|
|
#else
|
|
fd = -1;
|
|
flags |= MAP_ANONYMOUS;
|
|
#endif
|
|
|
|
return mmap(0, size, PROT_NONE, flags, fd, 0);
|
|
}
|
|
|
|
/*
|
|
* Activate memory in a reserved region from the given fd (if any), to make
|
|
* it accessible.
|
|
*/
|
|
static void *mmap_activate(void *ptr, size_t size, int fd,
|
|
uint32_t qemu_map_flags, off_t map_offset)
|
|
{
|
|
const bool noreserve = qemu_map_flags & QEMU_MAP_NORESERVE;
|
|
const bool readonly = qemu_map_flags & QEMU_MAP_READONLY;
|
|
const bool shared = qemu_map_flags & QEMU_MAP_SHARED;
|
|
const bool sync = qemu_map_flags & QEMU_MAP_SYNC;
|
|
const int prot = PROT_READ | (readonly ? 0 : PROT_WRITE);
|
|
int map_sync_flags = 0;
|
|
int flags = MAP_FIXED;
|
|
void *activated_ptr;
|
|
|
|
if (noreserve && !map_noreserve_effective(fd, qemu_map_flags)) {
|
|
return MAP_FAILED;
|
|
}
|
|
|
|
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
|
|
flags |= shared ? MAP_SHARED : MAP_PRIVATE;
|
|
flags |= noreserve ? MAP_NORESERVE : 0;
|
|
if (shared && sync) {
|
|
map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE;
|
|
}
|
|
|
|
activated_ptr = mmap(ptr, size, prot, flags | map_sync_flags, fd,
|
|
map_offset);
|
|
if (activated_ptr == MAP_FAILED && map_sync_flags) {
|
|
if (errno == ENOTSUP) {
|
|
char *proc_link = g_strdup_printf("/proc/self/fd/%d", fd);
|
|
char *file_name = g_malloc0(PATH_MAX);
|
|
int len = readlink(proc_link, file_name, PATH_MAX - 1);
|
|
|
|
if (len < 0) {
|
|
len = 0;
|
|
}
|
|
file_name[len] = '\0';
|
|
fprintf(stderr, "Warning: requesting persistence across crashes "
|
|
"for backend file %s failed. Proceeding without "
|
|
"persistence, data might become corrupted in case of host "
|
|
"crash.\n", file_name);
|
|
g_free(proc_link);
|
|
g_free(file_name);
|
|
warn_report("Using non DAX backing file with 'pmem=on' option"
|
|
" is deprecated");
|
|
}
|
|
/*
|
|
* If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, we will try
|
|
* again without these flags to handle backwards compatibility.
|
|
*/
|
|
activated_ptr = mmap(ptr, size, prot, flags, fd, map_offset);
|
|
}
|
|
return activated_ptr;
|
|
}
|
|
|
|
static inline size_t mmap_guard_pagesize(int fd)
|
|
{
|
|
#if defined(__powerpc64__) && defined(__linux__)
|
|
/* Mappings in the same segment must share the same page size */
|
|
return qemu_fd_getpagesize(fd);
|
|
#else
|
|
return qemu_real_host_page_size();
|
|
#endif
|
|
}
|
|
|
|
void *qemu_ram_mmap(int fd,
|
|
size_t size,
|
|
size_t align,
|
|
uint32_t qemu_map_flags,
|
|
off_t map_offset)
|
|
{
|
|
const size_t guard_pagesize = mmap_guard_pagesize(fd);
|
|
size_t offset, total;
|
|
void *ptr, *guardptr;
|
|
|
|
/*
|
|
* Note: this always allocates at least one extra page of virtual address
|
|
* space, even if size is already aligned.
|
|
*/
|
|
total = size + align;
|
|
|
|
guardptr = mmap_reserve(total, fd);
|
|
if (guardptr == MAP_FAILED) {
|
|
return MAP_FAILED;
|
|
}
|
|
|
|
assert(is_power_of_2(align));
|
|
/* Always align to host page size */
|
|
assert(align >= guard_pagesize);
|
|
|
|
offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
|
|
|
|
ptr = mmap_activate(guardptr + offset, size, fd, qemu_map_flags,
|
|
map_offset);
|
|
if (ptr == MAP_FAILED) {
|
|
munmap(guardptr, total);
|
|
return MAP_FAILED;
|
|
}
|
|
|
|
if (offset > 0) {
|
|
munmap(guardptr, offset);
|
|
}
|
|
|
|
/*
|
|
* Leave a single PROT_NONE page allocated after the RAM block, to serve as
|
|
* a guard page guarding against potential buffer overflows.
|
|
*/
|
|
total -= offset;
|
|
if (total > size + guard_pagesize) {
|
|
munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
|
|
}
|
|
|
|
return ptr;
|
|
}
|
|
|
|
void qemu_ram_munmap(int fd, void *ptr, size_t size)
|
|
{
|
|
if (ptr) {
|
|
/* Unmap both the RAM block and the guard page */
|
|
munmap(ptr, size + mmap_guard_pagesize(fd));
|
|
}
|
|
}
|