Re: [PATCH v1] xen/riscv: add initialization support for virtual SBI UART (vSBI UART)

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

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Hi Denis,

On 5/16/25 9:50 PM, dmkhn@proton.me wrote:
> Hi Oleksii,
>
> On Mon, May 12, 2025 at 05:55:21PM +0200, Oleksii Kurochko wrote:
>> This is the first step toward supporting a vSBI UART.
>>
>> The implementation checks for the presence of the "vsbi_uart" property
>> in the device tree. If present, the vSBI UART is initialized by:
>> - Allocating a structure that holds Xen console rings and character
>>    buffers.
>> - Initializing the vSBI UART spinlock.
>>
>> This commit introduces the following:
>> - domain_vsbi_uart_init() and domain_vsbi_uart_deinit() functions.
>> - A new arch_kernel_info structure with a vsbi_uart member.
>> - A vsbi_uart structure to hold information related to the vSBI
>>    driver, including:
>>    - Whether the vSBI UART backend is in the domain or in Xen.
>>    - If the backend is in Xen: details such as ring buffer, ring page,
>>      Xen console ring indexes, and character buffers.
>>    - A spinlock for synchronization.
>>
>> Also, introduce init_vuart() which is going to be called by dom0less
>> generic code during guest domain construction.
>>
>> Signed-off-by: Oleksii Kurochko<oleksii.kurochko@gmail.com>
> JFYI, I started to move all virtual UARTs under drivers/vuart directory
> and introducing a framework for hooking vUARTs into console driver.
>
> pl011 emulator cleanup
>    https://gitlab.com/xen-project/people/dmukhin/xen/-/commit/3c635962a349afed75f47cd2559a4160ffa41106
>
> original 'vuart' for hwdom cleanup
>    https://gitlab.com/xen-project/people/dmukhin/xen/-/commit/405c86cbd6d55f5737dc9ccf9b8a8f370767e3f0
>
> move pl011 to drivers/vuart
>    https://gitlab.com/xen-project/people/dmukhin/xen/-/commit/4b5cdff118a2795278dfcc2c1b60423b46e85f27
>
> move 'vuart' for hwdom cleanup to drivers/vuart
>    https://gitlab.com/xen-project/people/dmukhin/xen/-/commit/d76c17b8056c1d500afd854a513403fc3774da51
>
> which is followed by vUART driver framework introduction (not posted):
>    https://gitlab.com/xen-project/people/dmukhin/xen/-/commit/ebc7e83650e5e3f68e5d734e5c475c6bcde626fa
>
> These patches ^^ are not posted, since I do already have enough patches on
> the mailing list which are in progress.
>
> I did this work along w/ NS16550 emulator on x86.
>
> IMO, it is worth delivering those patches first and then integrate SBI UART.

Agree, it makes sense. But If it will take a lot of time to upstream/merge then I prefer this patch
go first to not block RISC-V upstreaming.

Anyway, I will look at your changes tomorrow.

Thanks.

~ Oleksii

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