Re: [Qemu-devel] [PATCH] hostmem: fix reference to uninit mr

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/03/2017 05:13, Peter Xu wrote:
> Trying to get memory region size of an uninitialized memory region is
> probably not a good idea. Let's just do the alloc no matter what.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>

What is the effect of the bug?  The idea was to do the initialization
once only (memory_region_size ought to be 0 when the MR is
uninitialized; now it is ugly but it made more sense when MemoryRegion
was just a C struct and not a QOM object).

Paolo

> ---
>  backends/hostmem-file.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> index 42efb2f..a61d1bd 100644
> --- a/backends/hostmem-file.c
> +++ b/backends/hostmem-file.c
> @@ -39,6 +39,7 @@ static void
>  file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
>  {
>      HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
> +    gchar *path;
>  
>      if (!backend->size) {
>          error_setg(errp, "can't create backend with size 0");
> @@ -51,16 +52,12 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
>  #ifndef CONFIG_LINUX
>      error_setg(errp, "-mem-path not supported on this host");
>  #else
> -    if (!memory_region_size(&backend->mr)) {
> -        gchar *path;
> -        backend->force_prealloc = mem_prealloc;
> -        path = object_get_canonical_path(OBJECT(backend));
> -        memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
> -                                 path,
> -                                 backend->size, fb->share,
> -                                 fb->mem_path, errp);
> -        g_free(path);
> -    }
> +    backend->force_prealloc = mem_prealloc;
> +    path = object_get_canonical_path(OBJECT(backend));
> +    memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
> +                                     path, backend->size, fb->share,
> +                                     fb->mem_path, errp);
> +    g_free(path);
>  #endif
>  }
>  
>