This patch specifies the master/slave communication to support
device IOTLB implementation 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 | 56 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index b365047..048a4d6 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
+ Size: a 64-bit size
+ User address: a 64-bit user address
+ Permissions flags: a 8-bit bit field:
+ - Bit 0: Read access
+ - Bit 1: Write access
+ 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;
@@ -258,6 +276,30 @@ 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. 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
+update 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_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. On success, the master is expected to reply when the
+request has been handled (for example, on miss requests, once the device IOTLB
+has been updated) with a zero payload, non-zero otherwise.
+
Protocol features
-----------------
@@ -524,6 +566,20 @@ Message types
has been negotiated, and protocol feature bit
VHOST_USER_PROTOCOL_F_SLAVE_REQ
bit is present in VHOST_USER_GET_PROTOCOL_FEATURES.
+ * VHOST_USER_IOTLB_MSG
+
+ Id: 22
+ Equivalent ioctl: N/A (equivalent to VHOST_IOTLB_MSG message type)
+ Initiator: Master or slave
+
+ Send IOTLB messages with struct vhost_iotlb_msg as payload.
+ Master sends such requests to update and invalidate entries in the device
+ IOTLB. Slave sends such requests to notify of an IOTLB miss, or an IOTLB
+ access failure. The recipient 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.
+
VHOST_USER_PROTOCOL_F_REPLY_ACK:
-------------------------------
The original vhost-user specification only demands replies for certain
--
2.9.3
