Si-Wei Liu
2023-Jan-31 23:22 UTC
[PATCH v2 4/7] virtio: VIRTIO_DEVICE_F_MASK for all per-device features
Introduce VIRTIO_DEVICE_F_MASK bitmask used for identification of per-device features. Feature bits VIRTIO_TRANSPORT_F_START through VIRTIO_TRANSPORT_F_END are reserved for transport features hence are not counted as per-device features against the 64bit feature space. Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com> --- include/uapi/linux/virtio_config.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h index 3c05162..3bdc7ed 100644 --- a/include/uapi/linux/virtio_config.h +++ b/include/uapi/linux/virtio_config.h @@ -54,6 +54,14 @@ #define VIRTIO_TRANSPORT_F_START 28 #define VIRTIO_TRANSPORT_F_END 41 +/* + * Bitmask for all per-device features: feature bits VIRTIO_TRANSPORT_F_START + * through VIRTIO_TRANSPORT_F_END are unset, i.e. 0xfffffc000fffffff for + * all 64bit features + */ +#define VIRTIO_DEVICE_F_MASK (~0ULL << (VIRTIO_TRANSPORT_F_END + 1) | \ + ((1ULL << VIRTIO_TRANSPORT_F_START) - 1)) + #ifndef VIRTIO_CONFIG_NO_LEGACY /* Do we get callbacks when the ring is completely used, even if we've * suppressed them? */ -- 1.8.3.1
Michael S. Tsirkin
2023-Feb-02 17:29 UTC
[PATCH v2 4/7] virtio: VIRTIO_DEVICE_F_MASK for all per-device features
On Tue, Jan 31, 2023 at 03:22:22PM -0800, Si-Wei Liu wrote:> Introduce VIRTIO_DEVICE_F_MASK bitmask used for identification > of per-device features. Feature bits VIRTIO_TRANSPORT_F_START > through VIRTIO_TRANSPORT_F_END are reserved for transport > features hence are not counted as per-device features against > the 64bit feature space. > > Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com> > --- > include/uapi/linux/virtio_config.h | 8 ++++++++ > 1 file changed, 8 insertions(+)Pls don't add this in uapi, people tend to depend on this and then things fail when we extend virtio. For example this won't work with >64 feature bits.> > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h > index 3c05162..3bdc7ed 100644 > --- a/include/uapi/linux/virtio_config.h > +++ b/include/uapi/linux/virtio_config.h > @@ -54,6 +54,14 @@ > #define VIRTIO_TRANSPORT_F_START 28 > #define VIRTIO_TRANSPORT_F_END 41 > > +/* > + * Bitmask for all per-device features: feature bits VIRTIO_TRANSPORT_F_START > + * through VIRTIO_TRANSPORT_F_END are unset, i.e. 0xfffffc000fffffff for > + * all 64bit features > + */ > +#define VIRTIO_DEVICE_F_MASK (~0ULL << (VIRTIO_TRANSPORT_F_END + 1) | \ > + ((1ULL << VIRTIO_TRANSPORT_F_START) - 1)) > + > #ifndef VIRTIO_CONFIG_NO_LEGACY > /* Do we get callbacks when the ring is completely used, even if we've > * suppressed them? */ > -- > 1.8.3.1