Hi Stefano,
> On 6 Sep 2022, at 11:22 pm, Stefano Stabellini <[email protected]> wrote:
>
> On Tue, 6 Sep 2022, Rahul Singh wrote:
>> Introduce a new sub-node under /chosen node to establish static event
>> channel communication between domains on dom0less systems.
>>
>> An event channel will be created beforehand to allow the domains to
>> send notifications to each other.
>>
>> Signed-off-by: Rahul Singh <[email protected]>
>> ---
>> Changes in v4:
>> - move documentation to common place for evtchn node in booting.txt
>> - Add comment why we use dt_device_static_evtchn_created()
>> - check if dt_get_parent() returns NULL
>> - fold process_static_evtchn_node() in alloc_static_evtchn()
>> Changes in v3:
>> - use device-tree used_by to find the domain id of the evtchn node.
>> - add new static_evtchn_create variable in struct dt_device_node to
>> hold the information if evtchn is already created.
>> - fix minor comments
>> Changes in v2:
>> - no change
>> ---
>> docs/misc/arm/device-tree/booting.txt | 98 +++++++++++++++++
>
> I have just reviewed the binding, only three minor comments below.
> Everything looks good.
Thanks for reviewing the code.
>
>
>> xen/arch/arm/domain_build.c | 147 ++++++++++++++++++++++++++
>> xen/arch/arm/include/asm/setup.h | 1 +
>> xen/arch/arm/setup.c | 2 +
>> xen/include/xen/device_tree.h | 16 +++
>> 5 files changed, 264 insertions(+)
>>
>> diff --git a/docs/misc/arm/device-tree/booting.txt
>> b/docs/misc/arm/device-tree/booting.txt
>> index 1b0dca1454..c8329b73e5 100644
>> --- a/docs/misc/arm/device-tree/booting.txt
>> +++ b/docs/misc/arm/device-tree/booting.txt
>> @@ -382,3 +382,101 @@ device-tree:
>>
>> This will reserve a 512MB region starting at the host physical address
>> 0x30000000 to be exclusively used by DomU1.
>> +
>> +Static Event Channel
>> +====================
>> +The event channel communication will be established statically between two
>> +domains (dom0 and domU also). Event channel connection information between
>> +domains will be passed to Xen via the device tree node. The event channel
>> +will be created and established in Xen before the domain started. The domain
>> +doesn???t need to do any operation to establish a connection. Domain only
>
> doesn't
>
> better to use ASCII if possible
Ack.
>
>
>> +needs hypercall EVTCHNOP_send(local port) to send notifications to the
>> +remote guest.
>> +
>> +There is no need to describe the static event channel info in the domU
>> device
>> +tree. Static event channels are only useful in fully static configurations,
>> +and in those configurations, the domU device tree dynamically generated by
>> Xen
>> +is not needed.
>> +
>> +To enable the event-channel interface for domU guests include the
>> +"xen,enhanced = "no-xenstore"" property in the domU Xen device tree node.
>
> double ""
Ack.
>
>
>> +
>> +Under the "xen,domain" compatible node for domU, there needs to be sub-nodes
>> +with compatible "xen,evtchn" that describe the event channel connection
>> +between two domUs. For dom0, there needs to be sub-nodes with compatible
>> +"xen,evtchn" under the chosen node.
>> +
>> +The static event channel node has the following properties:
>> +
>> +- compatible
>> +
>> + "xen,evtchn"
>> +
>> +- xen,evtchn
>> +
>> + The property is tuples of two numbers
>> + (local-evtchn link-to-foreign-evtchn) where:
>> +
>> + local-evtchn is an integer value that will be used to allocate local
>> port
>> + for a domain to send and receive event notifications to/from the remote
>> + domain. Maximum supported value is 2^17 for FIFO ABI and 4096 for 2L
>> ABI.
>> + It is recommended to use low event channel IDs.
>> +
>> + link-to-foreign-evtchn is a single phandle to a remote evtchn to which
>> + local-evtchn will be connected.
>> +
>> +Example
>> +=======
>> +
>> +chosen {
>> +
>> + /* one sub-node per local event channel */
>
> It would be good to say that this is for dom0 in the comment, e.g.:
>
> /* this is for Dom0 */
Ack.
Regards,
Rahul
