Re: [PATCH v4 11/42] virtio: add legacy feature table support

From: Michael S. Tsirkin
Date: Tue Nov 25 2014 - 16:40:10 EST


On Tue, Nov 25, 2014 at 06:53:42PM +0100, Cornelia Huck wrote:
> On Tue, 25 Nov 2014 18:42:09 +0200
> "Michael S. Tsirkin" <mst@xxxxxxxxxx> 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 <mst@xxxxxxxxxx>
> > ---
> > 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 */
>
> ?

I prefer have separate feature tables: drivers (plural) have tables
(plural).

Agree?

> > + 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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