From: Xuewei Niu <niuxuewei97@gmail.com>
To: sgarzare@redhat.com, parav@nvidia.com, mst@redhat.com,
fupan.lfp@antgroup.com
Cc: virtio-comment@lists.linux.dev, Xuewei Niu <niuxuewei.nxw@antgroup.com>
Subject: [PATCH v6 RESEND] virtio-vsock: Add support for multi devices
Date: Mon, 24 Mar 2025 14:43:35 +0800 [thread overview]
Message-ID: <20250324064335.1845722-1-niuxuewei.nxw@antgroup.com> (raw)
This patch brings a new feature, called "multi devices", to the virtio
vsock. It introduces a "VIRTIO_VSOCK_F_MULTI_DEVICES" feature bit, and a
"device_order" field to the config for the virtio vsock.
== Motivition ==
Vsock is a lightweight and widely used data exchange mechanism between host
and guest. Currently, the virtio-vsock only supports one device, resulting
in the inability to enable more than one backend. For instance, two devices
are required: one to transfer data to the VMM via virtio-vsock, and another
to a user process via vhost-user-vsock.
Apart from that, a side gain is that theoretically the performance might be
improved since each device has its own queue. But it varies depending on
the implementation.
== Typical Usages ==
Assuming there are two virtio-vsock devices on the guest, with CIDs 3 and 4
respectively. And the device with CID 3 is default.
Connect to the host using the device with CID 3.
```c
// use default one (no bind)
fd = socket(AF_VSOCK);
connect(fd, 2, 1234);
n = write(fd, buffer);
// or bind explicitly
fd = socket(AF_VSOCK);
bind(fd, 3, -1);
connect(fd, 2, 1234);
n = write(fd, buffer);
```
Connect to the host using the device with CID 4.
```c
// must bind explicitly as the device with CID 4 is not default.
fd = socket(AF_VSOCK);
bind(fd, 4, -1);
connect(fd, 2, 1234);
n = write(fd, buffer);
```
The first version of multi-devices implementation is available at [1].
[1] https://lore.kernel.org/virtualization/20240517144607.2595798-1-niuxuewei.nxw@antgroup.com
Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>
---
device-types/vsock/description.tex | 30 ++++++++++++++++++++++++++++--
1 file changed, 28 insertions(+), 2 deletions(-)
diff --git a/device-types/vsock/description.tex b/device-types/vsock/description.tex
index 7d91d15..7d0cfe4 100644
--- a/device-types/vsock/description.tex
+++ b/device-types/vsock/description.tex
@@ -20,6 +20,7 @@ \subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits}
\item[VIRTIO_VSOCK_F_STREAM (0)] stream socket type is supported.
\item[VIRTIO_VSOCK_F_SEQPACKET (1)] seqpacket socket type is supported.
\item[VIRTIO_VSOCK_F_NO_IMPLIED_STREAM (2)] stream socket type is not implied.
+\item[VIRTIO_VSOCK_F_MULTI_DEVICES (3)] multiple devices feature is supported.
\end{description}
\drivernormative{\subsubsection}{Feature bits}{Device Types / Socket Device / Feature bits}
@@ -34,6 +35,12 @@ \subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits}
VIRTIO_VSOCK_F_NO_IMPLIED_STREAM, the driver MAY act as if
VIRTIO_VSOCK_F_STREAM has also been negotiated.
+The driver SHOULD ignore devices that do not have
+VIRTIO_VSOCK_F_MULTI_DEVICES if the feature has been negotiated.
+
+The driver SHOULD ignore all subsequent devices if a device without
+VIRTIO_VSOCK_F_MULTI_DEVICES is present.
+
\devicenormative{\subsubsection}{Feature bits}{Device Types / Socket Device / Feature bits}
The device SHOULD offer the VIRTIO_VSOCK_F_NO_IMPLIED_STREAM feature.
@@ -52,6 +59,7 @@ \subsection{Device configuration layout}\label{sec:Device Types / Socket Device
\begin{lstlisting}
struct virtio_vsock_config {
le64 guest_cid;
+ le16 device_order;
};
\end{lstlisting}
@@ -77,11 +85,27 @@ \subsection{Device configuration layout}\label{sec:Device Types / Socket Device
\hline
\end{tabular}
+The \field{device_order} is used to identify the default device. Up to
+65,535 devices can be supported due to the size.
+
+\devicenormative{\subsubsection}{Device configuration layout}{Device Types / Socket Device / Device configuration layout}
+
+The device MUST provide a distinct \field{device_order} if
+VIRTIO_VSOCK_F_MULTI_DEVICES feature has been negotiated.
+
+\drivernormative{\subsubsection}{Device configuration layout}{Device Types / Socket Device / Device configuration layout}
+
+The driver MUST treat the device with the lowest \field{device_order} as
+the default device.
+
\subsection{Device Initialization}\label{sec:Device Types / Socket Device / Device Initialization}
\begin{enumerate}
\item The guest's cid is read from \field{guest_cid}.
+\item If VIRTIO_VSOCK_F_MULTI_DEVICES has been negotiated, the device's
+order will be read from \field{device_order}.
+
\item Buffers are added to the event virtqueue to receive events from the device.
\item Buffers are added to the rx virtqueue to start receiving packets.
@@ -233,8 +257,10 @@ \subsubsection{Receive and Transmit}\label{sec:Device Types / Socket Device / De
\drivernormative{\paragraph}{Device Operation: Receive and Transmit}{Device Types / Socket Device / Device Operation / Receive and Transmit}
-The \field{guest_cid} configuration field MUST be used as the source CID when
-sending outgoing packets.
+If \field{src_cid} is missing in outgoing packets, the driver MUST assign
+one. If more than one device is present, the driver SHOULD use the default
+device's \field{guest_cid} configuration. Otherwise, the driver SHOULD use
+the \field{guest_cid} of the only available device.
A VIRTIO_VSOCK_OP_RST reply MUST be sent if a packet is received with an
unknown \field{type} value.
--
2.34.1
next reply other threads:[~2025-03-24 6:43 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-24 6:43 Xuewei Niu [this message]
2025-03-24 13:51 ` [PATCH v6 RESEND] virtio-vsock: Add support for multi devices Stefano Garzarella
2025-03-25 3:19 ` Xuewei Niu
2025-03-26 8:50 ` Stefano Garzarella
2025-03-26 10:00 ` Xuewei Niu
2025-03-26 10:32 ` Stefano Garzarella
2025-03-26 10:36 ` Stefano Garzarella
2025-03-26 2:59 ` Xuewei Niu
2025-03-26 9:03 ` Stefano Garzarella
2025-03-27 8:18 ` Xuewei Niu
2025-03-31 6:18 ` Xuewei Niu
2025-04-01 11:15 ` Stefano Garzarella
2025-04-07 2:17 ` Xuewei Niu
2025-04-08 13:34 ` Stefano Garzarella
2025-04-09 6:55 ` Xuewei Niu
2025-04-09 9:34 ` Stefano Garzarella
2025-04-10 3:05 ` Xuewei Niu
2025-04-10 7:21 ` Stefano Garzarella
2025-04-10 8:58 ` Xuewei Niu
2025-04-10 10:38 ` Stefano Garzarella
2025-04-10 10:47 ` Xuewei Niu
2025-04-10 10:49 ` Stefano Garzarella
2025-04-10 13:47 ` Michael S. Tsirkin
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