Add a document explaining the reconnect process, including what the
Userspace App needs to do and how it works with the kernel.
Signed-off-by: Cindy Lu <[email protected]>
---
Documentation/userspace-api/vduse.rst | 41 +++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/Documentation/userspace-api/vduse.rst b/Documentation/userspace-api/vduse.rst
index bdb880e01132..f903aed714d1 100644
--- a/Documentation/userspace-api/vduse.rst
+++ b/Documentation/userspace-api/vduse.rst
@@ -231,3 +231,44 @@ able to start the dataplane processing as follows:
after the used ring is filled.
For more details on the uAPI, please see include/uapi/linux/vduse.h.
+
+HOW VDUSE devices reconnectoin works
+------------------------------------
+1. What is reconnection?
+
+ When the userspace application loads, it should establish a connection
+ to the vduse kernel device. Sometimes,the userspace application exists,
+ and we want to support its restart and connect to the kernel device again
+
+2. How can I support reconnection in a userspace application?
+
+2.1 During initialization, the userspace application should first verify the
+ existence of the device "/dev/vduse/vduse_name".
+ If it doesn't exist, it means this is the first-time for connection. goto step 2.2
+ If it exists, it means this is a reconnection, and we should goto step 2.3
+
+2.2 Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on
+ /dev/vduse/control.
+ When ioctl(VDUSE_CREATE_DEV) is called, kernel allocates memory for
+ the reconnect information. The total memory size is PAGE_SIZE*vq_mumber.
+
+2.3 Check if the information is suitable for reconnect
+ If this is reconnection :
+ Before attempting to reconnect, The userspace application needs to use the
+ ioctl(VDUSE_DEV_GET_CONFIG, VDUSE_DEV_GET_STATUS, VDUSE_DEV_GET_FEATURES...)
+ to get the information from kernel.
+ Please review the information and confirm if it is suitable to reconnect.
+
+2.4 Userspace application needs to mmap the memory to userspace
+ The userspace application requires mapping one page for every vq. These pages
+ should be used to save vq-related information during system running. Additionally,
+ the application must define its own structure to store information for reconnection.
+
+2.5 Completed the initialization and running the application.
+ While the application is running, it is important to store relevant information
+ about reconnections in mapped pages. When calling the ioctl VDUSE_VQ_GET_INFO to
+ get vq information, it's necessary to check whether it's a reconnection. If it is
+ a reconnection, the vq-related information must be get from the mapped pages.
+
+2.6 When the Userspace application exits, it is necessary to unmap all the
+ pages for reconnection
--
2.43.0
On Fri, Mar 29, 2024 at 05:38:25PM +0800, Cindy Lu wrote:
> Add a document explaining the reconnect process, including what the
> Userspace App needs to do and how it works with the kernel.
>
> Signed-off-by: Cindy Lu <[email protected]>
> ---
> Documentation/userspace-api/vduse.rst | 41 +++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)
>
> diff --git a/Documentation/userspace-api/vduse.rst b/Documentation/userspace-api/vduse.rst
> index bdb880e01132..f903aed714d1 100644
> --- a/Documentation/userspace-api/vduse.rst
> +++ b/Documentation/userspace-api/vduse.rst
> @@ -231,3 +231,44 @@ able to start the dataplane processing as follows:
> after the used ring is filled.
>
> For more details on the uAPI, please see include/uapi/linux/vduse.h.
> +
> +HOW VDUSE devices reconnectoin works
typo
> +------------------------------------
> +1. What is reconnection?
> +
> + When the userspace application loads, it should establish a connection
> + to the vduse kernel device. Sometimes,the userspace application exists,
> + and we want to support its restart and connect to the kernel device again
> +
> +2. How can I support reconnection in a userspace application?
> +
> +2.1 During initialization, the userspace application should first verify the
> + existence of the device "/dev/vduse/vduse_name".
> + If it doesn't exist, it means this is the first-time for connection. goto step 2.2
> + If it exists, it means this is a reconnection, and we should goto step 2.3
> +
> +2.2 Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on
> + /dev/vduse/control.
> + When ioctl(VDUSE_CREATE_DEV) is called, kernel allocates memory for
> + the reconnect information. The total memory size is PAGE_SIZE*vq_mumber.
> +
> +2.3 Check if the information is suitable for reconnect
> + If this is reconnection :
> + Before attempting to reconnect, The userspace application needs to use the
> + ioctl(VDUSE_DEV_GET_CONFIG, VDUSE_DEV_GET_STATUS, VDUSE_DEV_GET_FEATURES...)
> + to get the information from kernel.
> + Please review the information and confirm if it is suitable to reconnect.
> +
> +2.4 Userspace application needs to mmap the memory to userspace
> + The userspace application requires mapping one page for every vq. These pages
> + should be used to save vq-related information during system running. Additionally,
> + the application must define its own structure to store information for reconnection.
> +
> +2.5 Completed the initialization and running the application.
> + While the application is running, it is important to store relevant information
> + about reconnections in mapped pages. When calling the ioctl VDUSE_VQ_GET_INFO to
> + get vq information, it's necessary to check whether it's a reconnection. If it is
> + a reconnection, the vq-related information must be get from the mapped pages.
> +
I don't get it. So this is just a way for the application to allocate
memory? Why do we need this new way to do it?
Why not just mmap a file anywhere at all?
> +2.6 When the Userspace application exits, it is necessary to unmap all the
> + pages for reconnection
> --
> 2.43.0
On Fri, Mar 29, 2024 at 5:52 PM Michael S. Tsirkin <[email protected]> wrote:
>
> On Fri, Mar 29, 2024 at 05:38:25PM +0800, Cindy Lu wrote:
> > Add a document explaining the reconnect process, including what the
> > Userspace App needs to do and how it works with the kernel.
> >
> > Signed-off-by: Cindy Lu <[email protected]>
> > ---
> > Documentation/userspace-api/vduse.rst | 41 +++++++++++++++++++++++++++
> > 1 file changed, 41 insertions(+)
> >
> > diff --git a/Documentation/userspace-api/vduse.rst b/Documentation/userspace-api/vduse.rst
> > index bdb880e01132..f903aed714d1 100644
> > --- a/Documentation/userspace-api/vduse.rst
> > +++ b/Documentation/userspace-api/vduse.rst
> > @@ -231,3 +231,44 @@ able to start the dataplane processing as follows:
> > after the used ring is filled.
> >
> > For more details on the uAPI, please see include/uapi/linux/vduse.h.
> > +
> > +HOW VDUSE devices reconnectoin works
>
> typo
>
Really sorry for this, I will send a new version
Thanks
Cindy
> > +------------------------------------
> > +1. What is reconnection?
> > +
> > + When the userspace application loads, it should establish a connection
> > + to the vduse kernel device. Sometimes,the userspace application exists,
> > + and we want to support its restart and connect to the kernel device again
> > +
> > +2. How can I support reconnection in a userspace application?
> > +
> > +2.1 During initialization, the userspace application should first verify the
> > + existence of the device "/dev/vduse/vduse_name".
> > + If it doesn't exist, it means this is the first-time for connection. goto step 2.2
> > + If it exists, it means this is a reconnection, and we should goto step 2.3
> > +
> > +2.2 Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on
> > + /dev/vduse/control.
> > + When ioctl(VDUSE_CREATE_DEV) is called, kernel allocates memory for
> > + the reconnect information. The total memory size is PAGE_SIZE*vq_mumber.
> > +
> > +2.3 Check if the information is suitable for reconnect
> > + If this is reconnection :
> > + Before attempting to reconnect, The userspace application needs to use the
> > + ioctl(VDUSE_DEV_GET_CONFIG, VDUSE_DEV_GET_STATUS, VDUSE_DEV_GET_FEATURES...)
> > + to get the information from kernel.
> > + Please review the information and confirm if it is suitable to reconnect.
> > +
> > +2.4 Userspace application needs to mmap the memory to userspace
> > + The userspace application requires mapping one page for every vq. These pages
> > + should be used to save vq-related information during system running. Additionally,
> > + the application must define its own structure to store information for reconnection.
> > +
> > +2.5 Completed the initialization and running the application.
> > + While the application is running, it is important to store relevant information
> > + about reconnections in mapped pages. When calling the ioctl VDUSE_VQ_GET_INFO to
> > + get vq information, it's necessary to check whether it's a reconnection. If it is
> > + a reconnection, the vq-related information must be get from the mapped pages.
> > +
>
>
> I don't get it. So this is just a way for the application to allocate
> memory? Why do we need this new way to do it?
> Why not just mmap a file anywhere at all?
>
We used to use tmpfs to save this reconnect information,
but this will make the API not self contained, so we changed to using
the kernel memory
Thanks
cindy
>
> > +2.6 When the Userspace application exits, it is necessary to unmap all the
> > + pages for reconnection
> > --
> > 2.43.0
>