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Subject[PATCH 2/3] vhost: add support for legacy virtio
From
Date
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
drivers/vhost/vhost.h | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

Michael,

The vhost_is_little_endian() helper adds unconditionnal overhead to fixed
endian architectures: that is all architectures except arm and ppc64. This
was addressed in QEMU with a TARGET_IS_BIENDIAN macro. Please give an
advice about how to address this in the vhost code.

Thanks.

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index ce2c68e..21e7d6a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -176,34 +176,42 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
return vq->acked_features & (1ULL << bit);
}

+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+ if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+ return true;
+ else
+ return !vq->legacy_big_endian;
+}
+
/* Memory accessors */
static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
{
- return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
}

static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
{
- return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
}

static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
{
- return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
}

static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
{
- return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
}

static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
{
- return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
}

static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
{
- return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+ return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
}
#endif


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