On Fri, Feb 20, 2015 at 11:07:39AM +0100, Greg Kurz wrote:
> The VHOST_VRING_F_LEGACY_BIG_ENDIAN flag informs the kernel that the
> associated device is big endian. Of course, this only makes sense for
> legacy virtio devices since modern virtio devices are always little
> endian.
>
> It will be used by the vhost memory accessors to byteswap vring data when
> we have a legacy device, in case host and guest endianness differ.
>
> Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/vhost/vhost.c | 6 +++++-
> drivers/vhost/vhost.h | 3 +++
> include/uapi/linux/vhost.h | 2 ++
> 3 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 2ee2826..dad3c37 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> vq->call = NULL;
> vq->log_ctx = NULL;
> vq->memory = NULL;
> + vq->legacy_big_endian = false;
> }
>
> static int vhost_worker(void *data)
> @@ -701,7 +702,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
> r = -EFAULT;
> break;
> }
> - if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
> + if (a.flags & ~(0x1 << VHOST_VRING_F_LOG|
> + 0x1 << VHOST_VRING_F_LEGACY_BIG_ENDIAN)) {
whitespace damage here
> r = -EOPNOTSUPP;
> break;
> }
need to also make sure LEGACY_BIG_ENDIAN isn't set with VERSION_1.
> @@ -751,6 +753,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
> vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
> vq->log_addr = a.log_guest_addr;
> vq->used = (void __user *)(unsigned long)a.used_user_addr;
> + vq->legacy_big_endian =
> + !!(a.flags & (0x1 << VHOST_VRING_F_LEGACY_BIG_ENDIAN));
> break;
> case VHOST_SET_VRING_KICK:
> if (copy_from_user(&f, argp, sizeof f)) {
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 8c1c792..ce2c68e 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -106,6 +106,9 @@ struct vhost_virtqueue {
> /* Log write descriptors */
> void __user *log_base;
> struct vhost_log *log;
> +
> + /* We need to know the device endianness with legacy virtio. */
> + bool legacy_big_endian;
> };
>
> struct vhost_dev {
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index bb6a5b4..0bf4491 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -34,6 +34,8 @@ struct vhost_vring_addr {
> /* Flag values: */
> /* Whether log address is valid. If set enables logging. */
> #define VHOST_VRING_F_LOG 0
> + /* Whether we have a big-endian legacy virtio device. */
> +#define VHOST_VRING_F_LEGACY_BIG_ENDIAN 1
>
> /* Start of array of descriptors (virtually contiguous) */
> __u64 desc_user_addr;
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