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

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Jan 09, 2014 at 03:59:55PM +0100, Antonios Motakis wrote:
> 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>

I like this approach and think it will work fine for my use-case, thanks.

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.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
> 
>