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vhost-user: support registering external host notifiers

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This patch introduces VHOST_USER_PROTOCOL_F_HOST_NOTIFIER.
With this feature negotiated, vhost-user backend can register
memory region based host notifiers. And it will allow the guest
driver in the VM to notify the hardware accelerator at the
vhost-user backend directly.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Tiwei Bie 2018-05-24 18:33:34 +08:00 • committed by Michael S. Tsirkin
parent 4d0cf552d3
commit 44866521bd
3 changed files with 154 additions and 0 deletions
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33
docs/interop/vhost-user.txt
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@ -132,6 +132,16 @@ Depending on the request type, payload can be:
Payload: Size bytes array holding the contents of the virtio
device's configuration space
* Vring area description
-----------------------
| u64 | size | offset |
-----------------------
u64: a 64-bit integer contains vring index and flags
Size: a 64-bit size of this area
Offset: a 64-bit offset of this area from the start of the
supplied file descriptor
In QEMU the vhost-user message is implemented with the following struct:
typedef struct VhostUserMsg {
@ -146,6 +156,7 @@ typedef struct VhostUserMsg {
VhostUserLog log;
struct vhost_iotlb_msg iotlb;
VhostUserConfig config;
VhostUserVringArea area;
};
} QEMU_PACKED VhostUserMsg;
@ -385,6 +396,7 @@ Protocol features
#define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
#define VHOST_USER_PROTOCOL_F_CONFIG 9
#define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
#define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
Master message types
--------------------
@ -782,6 +794,27 @@ Slave message types
the VHOST_USER_NEED_REPLY flag, master must respond with zero when
operation is successfully completed, or non-zero otherwise.
* VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG
Id: 3
Equivalent ioctl: N/A
Slave payload: vring area description
Master payload: N/A
Sets host notifier for a specified queue. The queue index is contained
in the u64 field of the vring area description. The host notifier is
described by the file descriptor (typically it's a VFIO device fd) which
is passed as ancillary data and the size (which is mmap size and should
be the same as host page size) and offset (which is mmap offset) carried
in the vring area description. QEMU can mmap the file descriptor based
on the size and offset to get a memory range. Registering a host notifier
means mapping this memory range to the VM as the specified queue's notify
MMIO region. Slave sends this request to tell QEMU to de-register the
existing notifier if any and register the new notifier if the request is
sent with a file descriptor.
This request should be sent only when VHOST_USER_PROTOCOL_F_HOST_NOTIFIER
protocol feature has been successfully negotiated.
VHOST_USER_PROTOCOL_F_REPLY_ACK:
-------------------------------
The original vhost-user specification only demands replies for certain