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[Qemu-devel] [PATCH 1/2] vhost: add VHOST_VRING_F_LEGACY_BIG_ENDIAN flag
From: |
Greg Kurz |
Subject: |
[Qemu-devel] [PATCH 1/2] vhost: add VHOST_VRING_F_LEGACY_BIG_ENDIAN flag |
Date: |
Fri, 20 Feb 2015 11:32:59 +0100 |
User-agent: |
StGit/0.17-dirty |
When the guest and the host have a different endian order, the data
being accessed in the vring queues needs to be byteswapped if we run
in legacy mode.
This patch adds a flag to inform the vhost kernel backend about the
endianness to use.
This patch is based on previous work by Cédric Le Goater.
Cc: Cédric Le Goater <address@hidden>
Signed-off-by: Greg Kurz <address@hidden>
---
hw/virtio/vhost.c | 10 +++++++++-
include/hw/virtio/vhost.h | 1 +
linux-headers/linux/vhost.h | 2 ++
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 5a12861..bd442f1 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -539,7 +539,13 @@ static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
.log_guest_addr = vq->used_phys,
.flags = enable_log ? (1 << VHOST_VRING_F_LOG) : 0,
};
- int r = dev->vhost_ops->vhost_call(dev, VHOST_SET_VRING_ADDR, &addr);
+ int r;
+
+ if (vq->legacy_big_endian) {
+ addr.flags |= (1 << VHOST_VRING_F_LEGACY_BIG_ENDIAN);
+ }
+
+ r = dev->vhost_ops->vhost_call(dev, VHOST_SET_VRING_ADDR, &addr);
if (r < 0) {
return -errno;
}
@@ -707,6 +713,8 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
goto fail_alloc_ring;
}
+ vq->legacy_big_endian = virtio_is_big_endian(vdev);
+
r = vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_enabled);
if (r < 0) {
r = -errno;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index d5593d1..991fa20 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -20,6 +20,7 @@ struct vhost_virtqueue {
unsigned long long ring_phys;
unsigned ring_size;
EventNotifier masked_notifier;
+ bool legacy_big_endian; /* Only used with legacy virtio devices */
};
typedef unsigned long vhost_log_chunk_t;
diff --git a/linux-headers/linux/vhost.h b/linux-headers/linux/vhost.h
index c656f61..ffbb8ee 100644
--- a/linux-headers/linux/vhost.h
+++ b/linux-headers/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;