On 05/11/2017 08:25 PM, Michael S. Tsirkin wrote:
On Thu, May 11, 2017 at 02:32:46PM +0200, Maxime Coquelin wrote:
This patch specifies and implements the master/slave communication
to support device IOTLB in slave.
The vhost_iotlb_msg structure introduced for kernel backends is
re-used, making the design close between the two backends.
An exception is the use of the secondary channel to enable the
slave to send IOTLB miss requests to the master.
Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
docs/specs/vhost-user.txt | 75 +++++++++++++++++++++++++++++++++++++++++++++++
hw/virtio/vhost-user.c | 31 ++++++++++++++++++++
2 files changed, 106 insertions(+)
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 5fa7016..4a1f0c3 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -97,6 +97,23 @@ Depending on the request type, payload can be:
log offset: offset from start of supplied file descriptor
where logging starts (i.e. where guest address 0 would be logged)
+ * An IOTLB message
+ ---------------------------------------------------------
+ | iova | size | user address | permissions flags | type |
+ ---------------------------------------------------------
+
+ IOVA: a 64-bit guest I/O virtual address
guest -> VM
Ok.
+ Size: a 64-bit size
How do you specify "all memory"? give special meaning to size 0?
Good point, it does not support all memory currently.
It is not vhost-user specific, but general to the vhost implementation.
+ User address: a 64-bit user address
+ Permissions flags: a 8-bit bit field:
+ - Bit 0: Read access
+ - Bit 1: Write access
Can both bits be set? Can none?
Both. I will change it by listing values directly:
- 0 : No access
- 1 : Read
- 2 : Write
- 3 : Read Write
+ Type: a 8-bit IOTLB message type:
+ - 1: IOTLB miss
+ - 2: IOTLB update
+ - 3: IOTLB invalidate
+ - 4: IOTLB access fail
+
In QEMU the vhost-user message is implemented with the following struct:
typedef struct VhostUserMsg {
@@ -109,6 +126,7 @@ typedef struct VhostUserMsg {
struct vhost_vring_addr addr;
VhostUserMemory memory;
VhostUserLog log;
+ struct vhost_iotlb_msg iotlb;
};
} QEMU_PACKED VhostUserMsg;
@@ -253,6 +271,31 @@ Once the source has finished migration, rings will be stopped by
the source. No further update must be done before rings are
restarted.
+IOMMU support
+-------------
+
+When the VIRTIO_F_IOMMU_PLATFORM feature has been negotiated, the master has
+to send IOTLB entries update & invalidation by sending VHOST_USER_IOTLB_MSG
+requests to the slave with a struct vhost_iotlb_msg payload.
Always? This seems a bit strange since iommu can be enabled/disabled
dynamically.
Ok, what about:
When the VIRTIO_F_IOMMU_PLATFORM feature has been negotiated and iommu
is enbaled, the master sends IOTLB entries update & invalidation via
VHOST_USER_IOTLB_MSG requests to the slave with a struct vhost_iotlb_msg
payload.
Closing channel seems like a wrong thing to do for this.
Sorry, I'm not sure to get your comment.
For update events,
+the iotlb payload has to be filled with the update message type (2), the I/O
+virtual address, the size, the user virtual address, and the permissions
+flags. For invalidation events, the iotlb payload has to be filled with the
+invalidation message type (3), the I/O virtual address and the size. On
+success, the slave is expected to reply with a zero payload, non-zero
+otherwise.
+
+When the VHOST_USER_PROTOCOL_F_SLAVE_REQ is supported by the slave, and the
+master initiated the slave to master communication channel using the
+VHOST_USER_SET_SLAVE_REQ_FD request, the slave can send IOTLB miss and access
+failure events by sending VHOST_USER_SLAVE_IOTLB_MSG requests to the master
+with a struct vhost_iotlb_msg payload. For miss events, the iotlb payload has
+to be filled with the miss message type (1), the I/O virtual address and the
+permissions flags. For access failure event, the iotlb payload has to be
+filled with the access failure message type (4), the I/O virtual address and
+the permissions flags. For synchronization purpose, the slave may rely on the
+reply-ack feature, so the master may send a reply when operation is completed
+if the reply-ack feature is negotiated and slaves requests a reply.
+
Slave communication
-------------------
@@ -514,6 +557,38 @@ Master message types
If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, slave must respond
with zero for success, non-zero otherwise.
+ * VHOST_USER_IOTLB_MSG
+
+ Id: 22
+ Equivalent ioctl: N/A (equivalent to VHOST_IOTLB_MSG message type)
+ Master payload: struct vhost_iotlb_msg
+ Slave payload: u64
+
+ Send IOTLB messages with struct vhost_iotlb_msg as payload.
+ Master sends such requests to update and invalidate entries in the device
+ IOTLB. The slave has to acknowledge the request with sending zero as u64
+ payload for success, non-zero otherwise.
+ This request should be send only when VIRTIO_F_IOMMU_PLATFORM feature
+ has been successfully negotiated.
+
+Slave message types
+-------------------
+
+ * VHOST_USER_SLAVE_IOTLB_MSG
+
+ Id: 1
+ Equivalent ioctl: N/A (equivalent to VHOST_IOTLB_MSG message type)
+ Slave payload: struct vhost_iotlb_msg
+ Master payload: N/A
+
+ Send IOTLB messages with struct vhost_iotlb_msg as payload.
+ Slave sends such requests to notify of an IOTLB miss, or an IOTLB
+ access failure. If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated,
+ and slave set the VHOST_USER_NEED_REPLY flag, master must respond with
+ zero when operation is successfully completed, or non-zero otherwise.
+ This request should be send only when VIRTIO_F_IOMMU_PLATFORM feature
+ has been successfully negotiated.
+
Are there limitations on number of messages in flight?
I didn't think about this, I would say the maximum number of messages in
flight is dependent on the socket buffer size (which is kept to default
in this series).
You question highlights a bug in by DPDK prototype, as the MISS request
can be sent by multiple threads, and I didn't protected this with a lock
to prevent concurrent read on the socket when waiting for the REPLY_ACK.
Thanks,
Maxime