Re: [Qemu-devel] [PATCH 09/15] loader: use mmap for ROMs

[Paolo Bonzini]

On 28/06/2016 11:01, Peter Lieven wrote:
> a classic use for mmap here.
> 
> Signed-off-by: Peter Lieven <address@hidden>

They are never freed, why does mmap help?

Paolo

> ---
>  hw/core/loader.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/core/loader.c b/hw/core/loader.c
> index 53e0e41..f217edc 100644
> --- a/hw/core/loader.c
> +++ b/hw/core/loader.c
> @@ -55,6 +55,7 @@
>  #include "exec/address-spaces.h"
>  #include "hw/boards.h"
>  #include "qemu/cutils.h"
> +#include "qemu/mmap-alloc.h"
>  
>  #include <zlib.h>
>  
> @@ -837,7 +838,7 @@ int rom_add_file(const char *file, const char *fw_dir,
>  {
>      MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
>      Rom *rom;
> -    int rc, fd = -1;
> +    int fd = -1;
>      char devpath[100];
>  
>      rom = g_malloc0(sizeof(*rom));
> @@ -867,12 +868,9 @@ int rom_add_file(const char *file, const char *fw_dir,
>      }
>  
>      rom->datasize = rom->romsize;
> -    rom->data     = g_malloc0(rom->datasize);
> -    lseek(fd, 0, SEEK_SET);
> -    rc = read(fd, rom->data, rom->datasize);
> -    if (rc != rom->datasize) {
> -        fprintf(stderr, "rom: file %-20s: read error: rc=%d (expected 
> %zd)\n",
> -                rom->name, rc, rom->datasize);
> +    rom->data     = mmap(NULL, rom->datasize, PROT_READ, MAP_SHARED, fd, 0);
> +    if (rom->data == MAP_FAILED) {
> +        fprintf(stderr, "rom: file %-20s: mmap error\n", rom->name);
>          goto err;
>      }
>      close(fd);
> @@ -915,7 +913,7 @@ err:
>      if (fd != -1)
>          close(fd);
>  
> -    g_free(rom->data);
> +    qemu_anon_ram_munmap(rom->data, rom->romsize);
>      g_free(rom->path);
>      g_free(rom->name);
>      if (fw_dir) {
> @@ -1013,7 +1011,7 @@ static void rom_reset(void *unused)
>          }
>          if (rom->isrom) {
>              /* rom needs to be written only once */
> -            g_free(rom->data);
> +            qemu_anon_ram_munmap(rom->data, rom->datasize);
>              rom->data = NULL;
>          }
>          /*
>