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

[Oleksii Kurochko]

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.cari...@microchip.com>
Signed-off-by: Oleksii Kurochko<oleksii.kuroc...@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.

--- /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<jbeul...@suse.com>

Thanks.

~ Oleksii