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

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

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@xxxxxxxxxxxxx>
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> >       
> 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.
> > --- /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. 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.

> With authorship clarified and this variable adjusted according to whatever
> the longer term use of it is
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>     
Thanks.
~ Oleksii