Re: [PATCH v5 1/8] xen/arm: introduce static shared memory

[Julien Grall <julien@xen.org>]

Hi Penny,

I have looked at the code and I have further questions about the binding.

On 20/06/2022 06:11, Penny Zheng wrote:
> ---
>   docs/misc/arm/device-tree/booting.txt | 120 ++++++++++++++++++++++++++
>   xen/arch/arm/Kconfig                  |   6 ++
>   xen/arch/arm/bootfdt.c                |  68 +++++++++++++++
>   xen/arch/arm/include/asm/setup.h      |   3 +
>   4 files changed, 197 insertions(+)
> 
> diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt
> index 98253414b8..6467bc5a28 100644
> --- a/docs/misc/arm/device-tree/booting.txt
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -378,3 +378,123 @@ device-tree:
>   
>   This will reserve a 512MB region starting at the host physical address
>   0x30000000 to be exclusively used by DomU1.
> +
> +Static Shared Memory
> +====================
> +
> +The static shared memory device tree nodes allow users to statically set up
> +shared memory on dom0less system, enabling domains to do shm-based
> +communication.
> +
> +- compatible
> +
> +    "xen,domain-shared-memory-v1"
> +
> +- xen,shm-id
> +
> +    An 8-bit integer that represents the unique identifier of the shared memory
> +    region. The maximum identifier shall be "xen,shm-id = <0xff>".

There is nothing in Xen that will ensure that xen,shm-id will match for 
all the nodes using the same region.

I see you write it to the guest device-tree. However there is a mismatch 
of the type: here you use an integer whereas the guest binding is using 
a string.

Cheers,

-- 
Julien Grall