Re: [PATCH v3 4/4] docs/features/dom0less: Update the late XenStore init protocol

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 17 May 2024, Henry Wang wrote:
> With the new allocation strategy of Dom0less DomUs XenStore page,
> update the doc of the late XenStore init protocol accordingly.
> 
> Signed-off-by: Henry Wang <xin.wang2@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> v3:
> - Wording change.
> v2:
> - New patch.
> ---
>  docs/features/dom0less.pandoc | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/docs/features/dom0less.pandoc b/docs/features/dom0less.pandoc
> index 725afa0558..8b178edee0 100644
> --- a/docs/features/dom0less.pandoc
> +++ b/docs/features/dom0less.pandoc
> @@ -110,9 +110,10 @@ hotplug PV drivers to dom0less guests. E.g. xl 
> network-attach domU.
>  The implementation works as follows:
>  - Xen allocates the xenstore event channel for each dom0less domU that
>    has the "xen,enhanced" property, and sets HVM_PARAM_STORE_EVTCHN
> -- Xen does *not* allocate the xenstore page and sets HVM_PARAM_STORE_PFN
> -  to ~0ULL (invalid)
> -- Dom0less domU kernels check that HVM_PARAM_STORE_PFN is set to invalid
> +- Xen allocates the xenstore page and sets HVM_PARAM_STORE_PFN as well
> +  as the connection status to XENSTORE_RECONNECT.
> +- Dom0less domU kernels check that HVM_PARAM_STORE_PFN is set to
> +  ~0ULL (invalid) or the connection status is *not* XENSTORE_CONNECTED.
>      - Old kernels will continue without xenstore support (Note: some old
>        buggy kernels might crash because they don't check the validity of
>        HVM_PARAM_STORE_PFN before using it! Disable "xen,enhanced" in
> @@ -121,13 +122,14 @@ The implementation works as follows:
>        channel (HVM_PARAM_STORE_EVTCHN) before continuing with the
>        initialization
>  - Once dom0 is booted, init-dom0less is executed:
> -    - it allocates the xenstore shared page and sets HVM_PARAM_STORE_PFN
> +    - it gets the xenstore shared page from HVM_PARAM_STORE_PFN
>      - it calls xs_introduce_domain
>  - Xenstored notices the new domain, initializes interfaces as usual, and
>    sends an event channel notification to the domain using the xenstore
>    event channel (HVM_PARAM_STORE_EVTCHN)
>  - The Linux domU kernel receives the event channel notification, checks
> -  HVM_PARAM_STORE_PFN again and continue with the initialization
> +  HVM_PARAM_STORE_PFN and the connection status again and continue with
> +  the initialization
>  
>  
>  Limitations
> -- 
> 2.34.1
> 
>