Re: [PATCH v2 3/4] xen/riscv: implement basic aplic_preinit()

[Jan Beulich <jbeulich@suse.com>]

On 26.03.2025 17:49, Oleksii Kurochko wrote:
> On 3/26/25 4:19 PM, Jan Beulich wrote:
>> On 25.03.2025 18:36, Oleksii Kurochko wrote:
>>> Introduce preinitialization stuff for the RISC-V Advanced Platform-Level
>>> Interrupt Controller (APLIC) in Xen:
>>>   - Implementing the APLIC pre-initialization function (`aplic_preinit()`),
>>>     ensuring that only one APLIC instance is supported in S mode.
>>>   - Initialize APLIC's correspoinding DT node.
>>>   - Declaring the DT device match table for APLIC.
>>>   - Setting `aplic_info.hw_version` during its declaration.
>>>   - Declaring an APLIC device.
>>>
>>> Since Microchip originally developed aplic.c [1], an internal discussion
>>> with them led to the decision to use the MIT license instead of the default
>>> GPL-2.0-only.
>>>
>>> [1]https://gitlab.com/xen-project/people/olkur/xen/-/commit/7cfb4bd4748ca268142497ac5c327d2766fb342d
>>>
>>> Signed-off-by: Romain Caritey<Romain.Caritey@microchip.com>
>>> Signed-off-by: Oleksii Kurochko<oleksii.kurochko@gmail.com>
>> You recall that From: != 1st S-o-b is unusual, and wants some explanation.
>> IOW it's unclear who the original author of this patch is.
> 
> I'm not 100% sure who should be the author. Such patch doesn't exist before but I took the changes
> based on the changes mentioned in commit message as [1].
> 
> If you think that the author should be Romain, I am okay with that.

I can't sensibly form an opinion here. This needs settling between him and you.
From your reply I'm not even convinced his S-o-b is legitimately there then.
You may want to use another, less standard tag in such a case (like the
Co-developed-by: that I've seen in use here and there) to still give credit to
him.

>>> --- /dev/null
>>> +++ b/xen/arch/riscv/aplic.c
>>> @@ -0,0 +1,49 @@
>>> +/* SPDX-License-Identifier: MIT */
>>> +
>>> +/*
>>> + * xen/arch/riscv/aplic.c
>>> + *
>>> + * RISC-V Advanced Platform-Level Interrupt Controller support
>>> + *
>>> + * Copyright (c) 2023-2024 Microchip.
>>> + * Copyright (c) 2024-2025 Vates
>>> + */
>>> +
>>> +#include <xen/errno.h>
>>> +#include <xen/init.h>
>>> +#include <xen/types.h>
>>> +
>>> +#include <asm/device.h>
>>> +#include <asm/intc.h>
>>> +
>>> +static struct intc_info aplic_info = {
>>> +    .hw_version = INTC_APLIC
>>> +};
>> Is this going to be written to (much) post-init? IOW - __read_mostly or
>> even __ro_after_init?
> 
> I think that __read_mostly would be better because intc_info structure in the future
> will contain member "void *private". And in `private` it can be a data which can
> be changed.

You mean the pointer can change? Or merely what it points to, i.e. ...

> For example, `private` can contain an aplic_priv structure:
> struct aplic_priv {
>      /* number of irqs */
>      uint32_t   nr_irqs;
> 
>      /* base physical address and size */
>      paddr_t    paddr_start;
>      paddr_t    paddr_end;
>      uint64_t   size;
> 
>      /* registers */
>      struct aplic_regs   *regs;
> 
>      /* imsic configuration */
>      const struct imsic_config *imsic_cfg;
> };
> 
> and regs from aplic_priv structure can be changed in runtime.

... the contents of such a struct? In this latter case the struct instance
here can still be __ro_after_init as long as the pointer is set from an
__init function.

Jan