[Qemu-devel] [PATCH v5 1/7] Convert -mem-path to QemuOpts and add prealloc, share and unlink properties

[Antonios Motakis <a.motakis@virtualopensystems.com>]

Extend -mem-path with additional properties:

 - prealloc=on|off - default off, same as -mem-prealloc
 - share=on|off - default off, memory is mmapped with MAP_SHARED flag
 - unlink=on|off - default on, inlink the file after openinng it

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
---
 exec.c                 | 57 +++++++++++++++++++++++++++++++++++++++++---------
 include/exec/cpu-all.h |  3 ---
 qemu-options.hx        | 10 +++++++--
 vl.c                   | 41 +++++++++++++++++++++++++++++++-----
 4 files changed, 91 insertions(+), 20 deletions(-)

diff --git a/exec.c b/exec.c
index 7e49e8e..30f4019 100644
--- a/exec.c
+++ b/exec.c
@@ -957,6 +957,7 @@ void qemu_mutex_unlock_ramlist(void)
 #include <sys/vfs.h>
 
 #define HUGETLBFS_MAGIC       0x958458f6
+#define MIN_HUGE_PAGE_SIZE    (2*1024*1024)
 
 static long gethugepagesize(const char *path)
 {
@@ -972,8 +973,9 @@ static long gethugepagesize(const char *path)
         return 0;
     }
 
-    if (fs.f_type != HUGETLBFS_MAGIC)
-        fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
+    if (fs.f_type != HUGETLBFS_MAGIC) {
+        return 0;
+    }
 
     return fs.f_bsize;
 }
@@ -994,11 +996,14 @@ static void *file_ram_alloc(RAMBlock *block,
     char *c;
     void *area;
     int fd;
+    int flags;
     unsigned long hpagesize;
+    QemuOpts *opts;
+    unsigned int mem_prealloc = 0, mem_share = 0, mem_unlink = 1;
 
     hpagesize = gethugepagesize(path);
     if (!hpagesize) {
-        return NULL;
+        hpagesize = MIN_HUGE_PAGE_SIZE;
     }
 
     if (memory < hpagesize) {
@@ -1010,6 +1015,14 @@ static void *file_ram_alloc(RAMBlock *block,
         return NULL;
     }
 
+    /* Fill config options */
+    opts = qemu_opts_find(qemu_find_opts("mem-path"), NULL);
+    if (opts) {
+        mem_prealloc = qemu_opt_get_bool(opts, "prealloc", 0);
+        mem_share = qemu_opt_get_bool(opts, "share", 0);
+        mem_unlink = qemu_opt_get_bool(opts, "unlink", 1);
+    }
+
     /* Make name safe to use with mkstemp by replacing '/' with '_'. */
     sanitized_name = g_strdup(block->mr->name);
     for (c = sanitized_name; *c != '\0'; c++) {
@@ -1017,20 +1030,28 @@ static void *file_ram_alloc(RAMBlock *block,
             *c = '_';
     }
 
-    filename = g_strdup_printf("%s/qemu_back_mem.%s.XXXXXX", path,
-                               sanitized_name);
+    filename = g_strdup_printf("%s/qemu_back_mem.%s%s", path, sanitized_name,
+                               (mem_unlink) ? ".XXXXXX" : "");
     g_free(sanitized_name);
 
-    fd = mkstemp(filename);
+    if (mem_unlink) {
+        fd = mkstemp(filename);
+    } else {
+        fd = open(filename, O_CREAT | O_RDWR | O_EXCL,
+                S_IRWXU | S_IRWXG | S_IRWXO);
+    }
     if (fd < 0) {
-        perror("unable to create backing store for hugepages");
+        perror("unable to create guest RAM backing store");
         g_free(filename);
         return NULL;
     }
-    unlink(filename);
+
+    if (mem_unlink) {
+        unlink(filename);
+    }
     g_free(filename);
 
-    memory = (memory+hpagesize-1) & ~(hpagesize-1);
+    memory = (memory + hpagesize - 1) & ~(hpagesize - 1);
 
     /*
      * ftruncate is not supported by hugetlbfs in older
@@ -1041,7 +1062,8 @@ static void *file_ram_alloc(RAMBlock *block,
     if (ftruncate(fd, memory))
         perror("ftruncate");
 
-    area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+    flags = mem_share ? MAP_SHARED : MAP_PRIVATE;
+    area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
     if (area == MAP_FAILED) {
         perror("file_ram_alloc: can't mmap RAM pages");
         close(fd);
@@ -1211,11 +1233,18 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                    MemoryRegion *mr)
 {
     RAMBlock *block, *new_block;
+    QemuOpts *opts;
+    const char *mem_path = 0;
 
     size = TARGET_PAGE_ALIGN(size);
     new_block = g_malloc0(sizeof(*new_block));
     new_block->fd = -1;
 
+    opts = qemu_opts_find(qemu_find_opts("mem-path"), NULL);
+    if (opts) {
+        mem_path = qemu_opt_get(opts, "path");
+    }
+
     /* This assumes the iothread lock is taken here too.  */
     qemu_mutex_lock_ramlist();
     new_block->mr = mr;
@@ -1348,6 +1377,14 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
     ram_addr_t offset;
     int flags;
     void *area, *vaddr;
+    QemuOpts *opts;
+    unsigned int mem_prealloc = 0;
+
+    /* Fill config options */
+    opts = qemu_opts_find(qemu_find_opts("mem-path"), NULL);
+    if (opts) {
+        mem_prealloc = qemu_opt_get_bool(opts, "prealloc", 0);
+    }
 
     QTAILQ_FOREACH(block, &ram_list.blocks, next) {
         offset = addr - block->offset;
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index b6998f0..4f8e989 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -467,9 +467,6 @@ typedef struct RAMList {
 } RAMList;
 extern RAMList ram_list;
 
-extern const char *mem_path;
-extern int mem_prealloc;
-
 /* Flags stored in the low bits of the TLB virtual address.  These are
    defined so that fast path ram access is all zeros.  */
 /* Zero if TLB entry is valid.  */
diff --git a/qemu-options.hx b/qemu-options.hx
index bcfe9ea..0d35c9c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -221,9 +221,15 @@ gigabytes respectively.
 ETEXI
 
 DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
-    "-mem-path FILE  provide backing storage for guest RAM\n", QEMU_ARCH_ALL)
+    "-mem-path [path=]path[,prealloc=on|off][,share=on|off][,unlink=on|off]\n"
+    "                provide backing storage for guest RAM\n"
+    "                path= a directory path for the backing store\n"
+    "                prealloc= preallocate guest memory [default disabled]\n"
+    "                share= enable mmap share flag [default disabled]\n"
+    "                unlink= enable unlinking the guest RAM files [default enabled]\n",
+        QEMU_ARCH_ALL)
 STEXI
-@item -mem-path @var{path}
+@item -mem-path [path=]@var{path}[,prealloc=on|off][,share=on|off][,unlink=on|off]
 @findex -mem-path
 Allocate guest RAM from a temporarily created file in @var{path}.
 ETEXI
diff --git a/vl.c b/vl.c
index 7511e70..4a52e0d 100644
--- a/vl.c
+++ b/vl.c
@@ -187,8 +187,6 @@ DisplayType display_type = DT_DEFAULT;
 static int display_remote;
 const char* keyboard_layout = NULL;
 ram_addr_t ram_size;
-const char *mem_path = NULL;
-int mem_prealloc = 0; /* force preallocation of physical target memory */
 int nb_nics;
 NICInfo nd_table[MAX_NICS];
 int autostart;
@@ -531,6 +529,31 @@ static QemuOptsList qemu_msg_opts = {
     },
 };
 
+static QemuOptsList qemu_mem_path_opts = {
+    .name = "mem-path",
+    .implied_opt_name = "path",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_mem_path_opts.head),
+    .desc = {
+        {
+            .name = "path",
+            .type = QEMU_OPT_STRING,
+        },
+        {
+            .name = "prealloc",
+            .type = QEMU_OPT_BOOL,
+        },
+        {
+            .name = "share",
+            .type = QEMU_OPT_BOOL,
+        },
+        {
+            .name = "unlink",
+            .type = QEMU_OPT_BOOL,
+        },
+        { /* end of list */ }
+    },
+};
+
 /**
  * Get machine options
  *
@@ -2892,6 +2915,7 @@ int main(int argc, char **argv, char **envp)
     qemu_add_opts(&qemu_tpmdev_opts);
     qemu_add_opts(&qemu_realtime_opts);
     qemu_add_opts(&qemu_msg_opts);
+    qemu_add_opts(&qemu_mem_path_opts);
 
     runstate_init();
 
@@ -3209,11 +3233,18 @@ int main(int argc, char **argv, char **envp)
                 break;
 #endif
             case QEMU_OPTION_mempath:
-                mem_path = optarg;
+                if (!qemu_opts_parse(qemu_find_opts("mem-path"), optarg, 1)) {
+                    exit(1);
+                }
                 break;
-            case QEMU_OPTION_mem_prealloc:
-                mem_prealloc = 1;
+            case QEMU_OPTION_mem_prealloc: {
+                QemuOpts *mem_opts = qemu_opts_find(qemu_find_opts("mem-path"),
+                                                    NULL);
+                if (mem_opts) {
+                    qemu_opt_set(mem_opts, "prealloc", "on");
+                }
                 break;
+            }
             case QEMU_OPTION_d:
                 log_mask = optarg;
                 break;
-- 
1.8.3.2