linux-kernel - Re: [PATCH -next v7 2/7] arm64: entry: Refactor the entry and exit for exceptions from EL1

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Message-ID: <df50cc99-027e-4182-ba4c-9837b354a062@arm.com>
Date: Tue, 5 Aug 2025 16:06:10 +0100
From: Ada Couprie Diaz <ada.coupriediaz@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@....com>, catalin.marinas@....com,
 will@...nel.org, oleg@...hat.com, sstabellini@...nel.org,
 mark.rutland@....com, puranjay@...nel.org, broonie@...nel.org,
 mbenes@...e.cz, ryan.roberts@....com, akpm@...ux-foundation.org,
 chenl311@...natelecom.cn, anshuman.khandual@....com,
 kristina.martsenko@....com, liaochang1@...wei.com, ardb@...nel.org,
 leitao@...ian.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: Re: [PATCH -next v7 2/7] arm64: entry: Refactor the entry and exit
 for exceptions from EL1

Hi,

On 29/07/2025 02:54, Jinjie Ruan wrote:

> The generic entry code uses irqentry_state_t to track lockdep and RCU
> state across exception entry and return. For historical reasons, arm64
> embeds similar fields within its pt_regs structure.
>
> In preparation for moving arm64 over to the generic entry code, pull
> these fields out of arm64's pt_regs, and use a separate structure,
> matching the style of the generic entry code.
>
> No functional changes.
As far as I understand and checked, we used the two fields
in an exclusive fashion, so there is indeed no functional change.
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
> [...]
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 8e798f46ad28..97e0741abde1 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> [...]
> @@ -475,73 +497,81 @@ UNHANDLED(el1t, 64, error)
>   static void noinstr el1_abort(struct pt_regs *regs, unsigned long esr)
>   {
>   	unsigned long far = read_sysreg(far_el1);
> +	arm64_irqentry_state_t state;
>   
> -	enter_from_kernel_mode(regs);
> +	state = enter_from_kernel_mode(regs);
Nit: There is some inconsistencies with some functions splitting state's 
definition
and declaration (like el1_abort here), while some others do it on the 
same line
(el1_undef() below for example).
In some cases it is welcome as the entry function is called after some 
other work,
but here for example it doesn't seem to be beneficial ?
>   	local_daif_inherit(regs);
>   	do_mem_abort(far, esr, regs);
>   	local_daif_mask();
> -	exit_to_kernel_mode(regs);
> +	exit_to_kernel_mode(regs, state);
>   }
>   
>   static void noinstr el1_pc(struct pt_regs *regs, unsigned long esr)
>   {
>   	unsigned long far = read_sysreg(far_el1);
> +	arm64_irqentry_state_t state;
>   
> -	enter_from_kernel_mode(regs);
> +	state = enter_from_kernel_mode(regs);
>   	local_daif_inherit(regs);
>   	do_sp_pc_abort(far, esr, regs);
>   	local_daif_mask();
> -	exit_to_kernel_mode(regs);
> +	exit_to_kernel_mode(regs, state);
>   }
>   
>   static void noinstr el1_undef(struct pt_regs *regs, unsigned long esr)
>   {
> -	enter_from_kernel_mode(regs);
> +	arm64_irqentry_state_t state = enter_from_kernel_mode(regs);
> +
>   	local_daif_inherit(regs);
>   	do_el1_undef(regs, esr);
>   	local_daif_mask();
> -	exit_to_kernel_mode(regs);
> +	exit_to_kernel_mode(regs, state);
>   }
>
> [...]
Other than the small nit:
Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@....com>