Nothing's wrong with vring_size as is, but it's nice to check that the new field in the avail ring won't overlow into the used ring.
Reported-by: Tom Lendacky <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]> --- include/linux/virtio_ring.h | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index 2a3b0ea..089cbf2 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -119,7 +119,13 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p, static inline unsigned vring_size(unsigned int num, unsigned long align) { - return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num) +#ifdef __KERNEL__ + /* Older versions did not have used_event field at the end of the + * avail ring. Used ring offset must be compatible with such devices. */ + size_t s = sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num); + BUG_ON(ALIGN(s, align) != ALIGN(s + sizeof(__u16), align)); +#endif + return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num) + align - 1) & ~(align - 1)) + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num; } -- 1.7.5.53.gc233e -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
