X-Git-Url: https://git.proxmox.com/?a=blobdiff_plain;f=util%2Fmmap-alloc.c;h=5ed7d29183ec8c8cc1eb8f6a664a34c4b04b1476;hb=e3feb2cc224f61149a27f021042f5a4230bb1008;hp=629d97a36244cacb12cc6ab890bb7f9c79a3454c;hpb=6f1d2d1c5ad20d464705b17318cb7ca495f8078a;p=mirror_qemu.git

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 629d97a362..5ed7d29183 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -9,8 +9,19 @@
  * 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/mmap-alloc.h"
+#include "qemu/host-utils.h"
+#include "qemu/cutils.h"
+#include "qemu/error-report.h"
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
@@ -33,20 +44,90 @@ size_t qemu_fd_getpagesize(int fd)
             return fs.f_bsize;
         }
     }
+#ifdef __sparc__
+    /* SPARC Linux needs greater alignment than the pagesize */
+    return QEMU_VMALLOC_ALIGN;
+#endif
 #endif
 
-    return getpagesize();
+    return qemu_real_host_page_size();
 }
 
-void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
+#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;
+
     /*
-     * Note: this always allocates at least one extra page of virtual address
-     * space, even if size is already aligned.
+     * 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.
      */
-    size_t total = size + align;
+    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
+    /*
+     * 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
@@ -54,56 +135,141 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
      * We do this unless we are using the system page size, in which case
      * anonymous memory is OK.
      */
-    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);
+    if (fd == -1 || qemu_fd_getpagesize(fd) == qemu_real_host_page_size()) {
+        fd = -1;
+        flags |= MAP_ANONYMOUS;
+    } else {
+        flags |= MAP_NORESERVE;
+    }
 #else
-    void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+    fd = -1;
+    flags |= MAP_ANONYMOUS;
 #endif
-    size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
-    void *ptr1;
 
-    if (ptr == MAP_FAILED) {
+    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;
     }
 
-    /* Make sure align is a power of 2 */
-    assert(!(align & (align - 1)));
-    /* Always align to host page size */
-    assert(align >= getpagesize());
-
-    ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
-                MAP_FIXED |
-                (fd == -1 ? MAP_ANONYMOUS : 0) |
-                (shared ? MAP_SHARED : MAP_PRIVATE),
-                fd, 0);
-    if (ptr1 == MAP_FAILED) {
-        munmap(ptr, total);
+    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;
     }
 
-    ptr += offset;
-    total -= offset;
+    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(ptr - offset, offset);
+        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.
      */
-    if (total > size + getpagesize()) {
-        munmap(ptr + size + getpagesize(), total - size - getpagesize());
+    total -= offset;
+    if (total > size + guard_pagesize) {
+        munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
     }
 
     return ptr;
 }
 
-void qemu_ram_munmap(void *ptr, size_t size)
+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 + getpagesize());
+        munmap(ptr, size + mmap_guard_pagesize(fd));
     }
 }