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[Qemu-devel] [PATCH v4 5/6] vhost: simplify vhost_needs_vring_endian()
From: |
Greg Kurz |
Subject: |
[Qemu-devel] [PATCH v4 5/6] vhost: simplify vhost_needs_vring_endian() |
Date: |
Fri, 05 Feb 2016 11:46:04 +0100 |
User-agent: |
StGit/0.17.1-dirty |
After the call to virtio_vdev_has_feature(), we only care for legacy
devices, so we don't need the extra check in virtio_is_big_endian().
Also the device_endian field is always set (VIRTIO_DEVICE_ENDIAN_UNKNOWN
may only happen on a virtio_load() path that cannot lead here), so we
don't need the assert() either.
This open codes the device_endian checking in vhost_needs_vring_endian().
It also adds a comment to explain the logic, as recent reviews showed the
cross-endian tweaks aren't that obvious.
Signed-off-by: Greg Kurz <address@hidden>
---
hw/virtio/vhost.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index bb17177f5e7e..9f8ac38ccf2d 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -749,6 +749,11 @@ static void vhost_log_stop(MemoryListener *listener,
/* FIXME: implement */
}
+/* The vhost driver natively knows how to handle the vrings of non
+ * cross-endian legacy devices and modern devices. Only legacy devices
+ * exposed to a bi-endian guest may require the vhost driver to use a
+ * specific endianness.
+ */
static inline bool vhost_needs_vring_endian(VirtIODevice *vdev)
{
if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
@@ -756,9 +761,9 @@ static inline bool vhost_needs_vring_endian(VirtIODevice
*vdev)
}
#ifdef TARGET_IS_BIENDIAN
#ifdef HOST_WORDS_BIGENDIAN
- return !virtio_is_big_endian(vdev);
+ return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
#else
- return virtio_is_big_endian(vdev);
+ return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
#endif
#else
return false;
- [Qemu-devel] [PATCH v4 0/6] virtio/vhost cross-endian cleanup, Greg Kurz, 2016/02/05
- [Qemu-devel] [PATCH v4 1/6] virtio-net: use the backend cross-endian capabilities, Greg Kurz, 2016/02/05
- [Qemu-devel] [PATCH v4 2/6] vhost-net: revert support of cross-endian vnet headers, Greg Kurz, 2016/02/05
- [Qemu-devel] [PATCH v4 3/6] virtio: move cross-endian helper to vhost, Greg Kurz, 2016/02/05
- [Qemu-devel] [PATCH v4 4/6] vhost: move virtio 1.0 check to cross-endian helper, Greg Kurz, 2016/02/05
- [Qemu-devel] [PATCH v4 5/6] vhost: simplify vhost_needs_vring_endian(),
Greg Kurz <=
- [Qemu-devel] [PATCH v4 6/6] virtio: optimize virtio_access_is_big_endian() for little-endian targets, Greg Kurz, 2016/02/05
- Re: [Qemu-devel] [PATCH v4 0/6] virtio/vhost cross-endian cleanup, Laurent Vivier, 2016/02/05
- Re: [Qemu-devel] [PATCH v4 0/6] virtio/vhost cross-endian cleanup, Laurent Vivier, 2016/02/10