From: Michael S. Tsirkin <mst@redhat.com>
Date: Tue, 27 Oct 2015 09:37:39 +0000 (+0200)
Subject: vhost: fix performance on LE hosts
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=e407f39afdc0741dcf20aed100b8e738ccab7cb1;p=openwrt%2Fstaging%2Fblogic.git

vhost: fix performance on LE hosts

commit 2751c9882b947292fcfb084c4f604e01724af804 ("vhost: cross-endian
support for legacy devices") introduced a minor regression: even with
cross-endian disabled, and even on LE host, vhost_is_little_endian is
checking is_le flag so there's always a branch.

To fix, simply check virtio_legacy_is_little_endian first.

Cc: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 4772862b71a7..d3f767448a72 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -183,10 +183,17 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
 	return vq->acked_features & (1ULL << bit);
 }
 
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
 static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
 {
 	return vq->is_le;
 }
+#else
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+	return virtio_legacy_is_little_endian() || vq->is_le;
+}
+#endif
 
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)