linux-kernel - Re: [PATCH -next v6 8/8] arm64: entry: Switch to generic IRQ entry

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Message-ID: <xhsmh4j0fl0p3.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Thu, 27 Feb 2025 19:08:56 +0100
From: Valentin Schneider <vschneid@...hat.com>
To: Jinjie Ruan <ruanjinjie@...wei.com>, catalin.marinas@....com,
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Cc: ruanjinjie@...wei.com
Subject: Re: [PATCH -next v6 8/8] arm64: entry: Switch to generic IRQ entry

On 13/02/25 21:00, Jinjie Ruan wrote:
> Currently, x86, Riscv, Loongarch use the generic entry. Convert arm64
> to use the generic entry infrastructure from kernel/entry/*.
> The generic entry makes maintainers' work easier and codes
> more elegant.
>
> Switch arm64 to generic IRQ entry first, which removed duplicate 100+
> LOC and make Lazy preemption on arm64 available by adding a
> _TIF_NEED_RESCHED_LAZY bit and enabling ARCH_HAS_PREEMPT_LAZY.

Just a drive-by comment as I'm interested in lazy preemption for arm64;
this series doesn't actually enable lazy preemption, is that for a
follow-up with the rest of the generic entry stuff?

>From a quick glance, it looks like everything is in place for enabling it.

> The next
> patch serise will switch to generic entry completely later. Switch to
> generic entry in two steps according to Mark's suggestion will make it
> easier to review.
>
> The changes are below:
>  - Remove *enter_from/exit_to_kernel_mode(), and wrap with generic
>    irqentry_enter/exit(). Also remove *enter_from/exit_to_user_mode(),
>    and wrap with generic enter_from/exit_to_user_mode() because they
>    are exactly the same so far.
>
>  - Remove arm64_enter/exit_nmi() and use generic irqentry_nmi_enter/exit()
>    because they're exactly the same, so the temporary arm64 version
>    irqentry_state can also be removed.
>
>  - Remove PREEMPT_DYNAMIC code, as generic entry do the same thing
>    if arm64 implement arch_irqentry_exit_need_resched().