Re: [Qemu-devel] [PATCH] Error on O_DIRECT for physical CDROM/DVD drives

["David S. Ahern" <daahern@cisco.com>]

On 07/20/10 10:09, Jes.Sorensen@redhat.com wrote:
> From: Jes Sorensen <Jes.Sorensen@redhat.com>
> 
> O_DIRECT (cache=none) requires sector alignment, however the physical
> sector size of CDROM/DVD drives is 2048, as opposed to most disk
> devices which use 512. QEMU is hard coding 512 all over the place, so
> allowing O_DIRECT for CDROM/DVD devices does not work. Exit with an
> error!
> 
> Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
> ---
>  block/raw-posix.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 291699f..1b840c4 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1139,6 +1139,11 @@ static int cdrom_open(BlockDriverState *bs, const char *filename, int flags)
>      BDRVRawState *s = bs->opaque;
>  
>      s->type = FTYPE_CD;
> +    if (flags & BDRV_O_NOCACHE) {
> +        fprintf(stderr, "O_DIRECT (cache=none) for CDROM/DVD device (%s) "
> +                "is unsupported\n", filename);
> +        exit(1);
> +    }

If a cdrom is added via the monitor this would abruptly terminate the VM
- which is not good.

David

>  
>      /* open will not fail even if no CD is inserted, so add O_NONBLOCK */
>      return raw_open_common(bs, filename, flags, O_NONBLOCK);