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vhost-user: fix legacy cross-endian configurations

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Currently, vhost-user does not implement any means for notifying the
backend about guest endianess. This commit introduces a new message
called VHOST_USER_SET_VRING_ENDIAN which is analogous to the ioctl()
called VHOST_SET_VRING_ENDIAN used for kernel vhost backends. Such
message is necessary for backends supporting legacy (pre-1.0) virtio
devices running in big-endian guests.

Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Signed-off-by: Mike Cui <cui@nutanix.com>
This commit is contained in:
Felipe Franciosi 2017-06-14 18:44:38 +01:00 • committed by Michael S. Tsirkin
parent 08b9e0ba62
commit 5df04f1762
2 changed files with 37 additions and 2 deletions
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16
docs/interop/vhost-user.txt
View file

@ -326,6 +326,7 @@ Protocol features
#define VHOST_USER_PROTOCOL_F_REPLY_ACK 3
#define VHOST_USER_PROTOCOL_F_MTU 4
#define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5
#define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
Master message types
--------------------
@ -580,6 +581,21 @@ Master message types
This request should be send only when VIRTIO_F_IOMMU_PLATFORM feature
has been successfully negotiated.
* VHOST_USER_SET_VRING_ENDIAN
Id: 23
Equivalent ioctl: VHOST_SET_VRING_ENDIAN
Master payload: vring state description
Set the endianess of a VQ for legacy devices. Little-endian is indicated
with state.num set to 0 and big-endian is indicated with state.num set
to 1. Other values are invalid.
This request should be sent only when VHOST_USER_PROTOCOL_F_CROSS_ENDIAN
has been negotiated.
Backends that negotiated this feature should handle both endianesses
and expect this message once (per VQ) during device configuration
(ie. before the master starts the VQ).
Slave message types
-------------------