On Tue, 25 Nov 2014 18:42:09 +0200
"Michael S. Tsirkin" <m...@redhat.com> wrote:

> virtio blk has some legacy feature bits that modern drivers

virtio-blk

> must not negotiate, but are needed for old legacy hosts
> (e.g. that dn't support virtio scsi).

(that e.g. don't support virtio-scsi)

> Allow a separate legacy feature table for such cases.
> 
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> ---
>  include/linux/virtio.h  |  4 ++++
>  drivers/virtio/virtio.c | 25 ++++++++++++++++++++++++-
>  2 files changed, 28 insertions(+), 1 deletion(-)
> 

> @@ -177,7 +185,22 @@ static int virtio_dev_probe(struct device *_d)
>               driver_features |= (1ULL << f);
>       }
> 
> -     dev->features = driver_features & device_features;
> +     /* Some drivers have a separate feature tables for virtio v1.0 */

/* some drivers have a separate feature table for legacy virtio */

?

> +     if (drv->feature_table_legacy) {
> +             driver_features_legacy = 0;
> +             for (i = 0; i < drv->feature_table_size_legacy; i++) {
> +                     unsigned int f = drv->feature_table_legacy[i];
> +                     BUG_ON(f >= 64);
> +                     driver_features_legacy |= (1ULL << f);
> +             }
> +     } else {
> +             driver_features_legacy = driver_features;
> +     }
(...)

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