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authorMaxime Coquelin <maxime.coquelin@redhat.com>2017-06-02 12:18:31 +0200
committerMichael S. Tsirkin <mst@redhat.com>2017-06-02 18:57:17 +0300
commit6dcdd06e3b0d0c5651219013ec975348e2050041 (patch)
tree38c78feaf354a78b5ba2853a5b66cdaf102e8f67 /docs/specs
parent4bbeeba023f22c117d7a4c561354b91a0bf62e42 (diff)
spec/vhost-user spec: Add IOMMU support
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.coquelin@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'docs/specs')
-rw-r--r--docs/specs/vhost-user.txt84
1 files changed, 84 insertions, 0 deletions
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 5fa7016cc1..481ab56e35 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -97,6 +97,25 @@ 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 I/O virtual address programmed by the guest
+ Size: a 64-bit size
+ User address: a 64-bit user address
+ Permissions: a 8-bit value:
+ - 0: No access
+ - 1: Read access
+ - 2: Write access
+ - 3: Read/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 +128,7 @@ typedef struct VhostUserMsg {
struct vhost_vring_addr addr;
VhostUserMemory memory;
VhostUserLog log;
+ struct vhost_iotlb_msg iotlb;
};
} QEMU_PACKED VhostUserMsg;
@@ -253,6 +273,38 @@ 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
+sends IOTLB entries update & invalidation by sending VHOST_USER_IOTLB_MSG
+requests to the slave with a struct vhost_iotlb_msg as 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. Addresses and size must be within vhost memory regions set
+via the VHOST_USER_SET_MEM_TABLE request. 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.
+
+The slave relies on the slave communcation channel (see "Slave communication"
+section below) to send IOTLB miss and access failure events, by sending
+VHOST_USER_SLAVE_IOTLB_MSG requests to the master with a struct vhost_iotlb_msg
+as 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. For miss events, completed
+operation means either master sent an update message containing the IOTLB entry
+containing requested address and permission, or master sent nothing if the IOTLB
+miss message is invalid (invalid IOVA or permission).
+
+The master isn't expected to take the initiative to send IOTLB update messages,
+as the slave sends IOTLB miss messages for the guest virtual memory areas it
+needs to access.
+
Slave communication
-------------------
@@ -514,6 +566,38 @@ 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.
+
VHOST_USER_PROTOCOL_F_REPLY_ACK:
-------------------------------
The original vhost-user specification only demands replies for certain