linux-kernel - Re: [PATCH RFC 18/22] LoongArch: Switch over to GENERIC_CPU

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Message-ID: <227771fa-1f22-4b9d-81f5-709f4f0c68c9@redhat.com>
Date:   Mon, 13 Nov 2023 14:20:55 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev,
        x86@...nel.org, linux-csky@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-parisc@...r.kernel.org
Cc:     Salil Mehta <salil.mehta@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com,
        James Morse <james.morse@....com>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>
Subject: Re: [PATCH RFC 18/22] LoongArch: Switch over to GENERIC_CPU_DEVICES

On 11/7/23 20:30, Russell King (Oracle) wrote:
> From: James Morse <james.morse@....com>
> 
> Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
> overridden by the arch code, switch over to this to allow common code
> to choose when the register_cpu() call is made.
> 
> This allows topology_init() to be removed.
> 
> This is an intermediate step to the logic being moved to drivers/acpi,
> where GENERIC_CPU_DEVICES will do the work when booting with acpi=off.
> 
> This is a subtle change. Originally:
> - on boot, topology_init() would have marked present CPUs that
>    io_master() is true for as hotplug-incapable.
> - if a CPU is hotplugged that is an io_master(), it can later be
>    hot-unplugged.
> 
> The new behaviour is that any CPU that io_master() is true for will
> now always be marked as hotplug-incapable, thus even if it was
> hotplugged, it can no longer be hot-unplugged.
> 
> This patch also has the effect of moving the registration of CPUs from
> subsys to driver core initialisation, prior to any initcalls running.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> ---
> Changes since RFC v2:
>   * Explain the change in behaviour in the patch description
>     (highlighted by Jonathan Cameron - thanks.) Add note about
>     initialisation order change.
> ---
>   arch/loongarch/Kconfig           |  1 +
>   arch/loongarch/kernel/topology.c | 29 ++---------------------------
>   2 files changed, 3 insertions(+), 27 deletions(-)
> 

Reviewed-by: Gavin Shan <gshan@...hat.com>