| Message ID | aacced20b8109a615ee24c1bde6d9f5702850111.1304541919.git.mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wednesday, May 04, 2011 03:51:09 PM Michael S. Tsirkin wrote: > Define a new feature bit for the guest to utilize a used_event index > (like Xen) instead if a flag bit to enable/disable interrupts. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > include/linux/virtio_ring.h | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h > index e4d144b..f5c1b75 100644 > --- a/include/linux/virtio_ring.h > +++ b/include/linux/virtio_ring.h > @@ -29,6 +29,10 @@ > /* We support indirect buffer descriptors */ > #define VIRTIO_RING_F_INDIRECT_DESC 28 > > +/* The Guest publishes the used index for which it expects an interrupt > + * at the end of the avail ring. Host should ignore the avail->flags > field. */ +#define VIRTIO_RING_F_USED_EVENT_IDX 29 > + > /* Virtio ring descriptors: 16 bytes. These can chain together via > "next". */ struct vring_desc { > /* Address (guest-physical). */ > @@ -83,6 +87,7 @@ struct vring { > * __u16 avail_flags; > * __u16 avail_idx; > * __u16 available[num]; > + * __u16 used_event_idx; > * > * // Padding to the next align boundary. > * char pad[]; > @@ -93,6 +98,10 @@ struct vring { > * struct vring_used_elem used[num]; > * }; > */ > +/* We publish the used event index at the end of the available ring. > + * It is at the end for backwards compatibility. */ > +#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) > + > static inline void vring_init(struct vring *vr, unsigned int num, void *p, > unsigned long align) > { You should update the vring_size procedure to account for the extra field at the end of the available ring by change the "(2 + num)" to "(3 + num)": return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num) Tom -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 04, 2011 at 04:56:09PM -0500, Tom Lendacky wrote: > On Wednesday, May 04, 2011 03:51:09 PM Michael S. Tsirkin wrote: > > Define a new feature bit for the guest to utilize a used_event index > > (like Xen) instead if a flag bit to enable/disable interrupts. > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > include/linux/virtio_ring.h | 9 +++++++++ > > 1 files changed, 9 insertions(+), 0 deletions(-) > > > > diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h > > index e4d144b..f5c1b75 100644 > > --- a/include/linux/virtio_ring.h > > +++ b/include/linux/virtio_ring.h > > @@ -29,6 +29,10 @@ > > /* We support indirect buffer descriptors */ > > #define VIRTIO_RING_F_INDIRECT_DESC 28 > > > > +/* The Guest publishes the used index for which it expects an interrupt > > + * at the end of the avail ring. Host should ignore the avail->flags > > field. */ +#define VIRTIO_RING_F_USED_EVENT_IDX 29 > > + > > /* Virtio ring descriptors: 16 bytes. These can chain together via > > "next". */ struct vring_desc { > > /* Address (guest-physical). */ > > @@ -83,6 +87,7 @@ struct vring { > > * __u16 avail_flags; > > * __u16 avail_idx; > > * __u16 available[num]; > > + * __u16 used_event_idx; > > * > > * // Padding to the next align boundary. > > * char pad[]; > > @@ -93,6 +98,10 @@ struct vring { > > * struct vring_used_elem used[num]; > > * }; > > */ > > +/* We publish the used event index at the end of the available ring. > > + * It is at the end for backwards compatibility. */ > > +#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) > > + > > static inline void vring_init(struct vring *vr, unsigned int num, void *p, > > unsigned long align) > > { > > You should update the vring_size procedure to account for the extra field at > the end of the available ring by change the "(2 + num)" to "(3 + num)": > return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num) > > Tom In practice it gives the same result because of the alignment, but sure. Thanks!
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index e4d144b..f5c1b75 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -29,6 +29,10 @@ /* We support indirect buffer descriptors */ #define VIRTIO_RING_F_INDIRECT_DESC 28 +/* The Guest publishes the used index for which it expects an interrupt + * at the end of the avail ring. Host should ignore the avail->flags field. */ +#define VIRTIO_RING_F_USED_EVENT_IDX 29 + /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ struct vring_desc { /* Address (guest-physical). */ @@ -83,6 +87,7 @@ struct vring { * __u16 avail_flags; * __u16 avail_idx; * __u16 available[num]; + * __u16 used_event_idx; * * // Padding to the next align boundary. * char pad[]; @@ -93,6 +98,10 @@ struct vring { * struct vring_used_elem used[num]; * }; */ +/* We publish the used event index at the end of the available ring. + * It is at the end for backwards compatibility. */ +#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) + static inline void vring_init(struct vring *vr, unsigned int num, void *p, unsigned long align) {
Define a new feature bit for the guest to utilize a used_event index (like Xen) instead if a flag bit to enable/disable interrupts. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- include/linux/virtio_ring.h | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)