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Date: Thu, 27 Feb 2014 19:30:26 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] file_ram_alloc: unify mem-path,
	mem-prealloc error handling
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To: Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, kvm-devel <kvm@vger.kernel.org>

Il 04/02/2014 19:41, Marcelo Tosatti ha scritto:
>
> -mem-prealloc asks to preallocate memory residing on -mem-path path.
>
> Currently QEMU exits in case:
>
> - Memory file has been created but allocation via explicit write
> fails.
>
> And it fallbacks to malloc in case:
> - Querying huge page size fails.
> - Lack of sync MMU support.
> - Open fails.
> - mmap fails.
>
> Have the same behaviour for all cases: fail in case -mem-path and
> -mem-prealloc are specified for regions where the requested size is
> suitable for hugepages.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Once we introduce memdev, I believe -mem-path should always exit, and 
never fall back to malloc/MAP_ANON.

For 2.0, I'm applying the patch to uq/master.

Paolo

> diff --git a/exec.c b/exec.c
> index 9ad0a4b..1da1ba7 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -996,7 +996,7 @@ static void *file_ram_alloc(RAMBlock *block,
>
>      hpagesize = gethugepagesize(path);
>      if (!hpagesize) {
> -        return NULL;
> +        goto error;
>      }
>
>      if (memory < hpagesize) {
> @@ -1005,7 +1005,7 @@ static void *file_ram_alloc(RAMBlock *block,
>
>      if (kvm_enabled() && !kvm_has_sync_mmu()) {
>          fprintf(stderr, "host lacks kvm mmu notifiers, -mem-path unsupported\n");
> -        return NULL;
> +        goto error;
>      }
>
>      /* Make name safe to use with mkstemp by replacing '/' with '_'. */
> @@ -1023,7 +1023,7 @@ static void *file_ram_alloc(RAMBlock *block,
>      if (fd < 0) {
>          perror("unable to create backing store for hugepages");
>          g_free(filename);
> -        return NULL;
> +        goto error;
>      }
>      unlink(filename);
>      g_free(filename);
> @@ -1043,7 +1043,7 @@ static void *file_ram_alloc(RAMBlock *block,
>      if (area == MAP_FAILED) {
>          perror("file_ram_alloc: can't mmap RAM pages");
>          close(fd);
> -        return (NULL);
> +        goto error;
>      }
>
>      if (mem_prealloc) {
> @@ -1087,6 +1087,12 @@ static void *file_ram_alloc(RAMBlock *block,
>
>      block->fd = fd;
>      return area;
> +
> +error:
> +    if (mem_prealloc) {
> +        exit(1);
> +    }
> +    return NULL;
>  }
>  #else
>  static void *file_ram_alloc(RAMBlock *block,
>