linux-kernel - Re: [PATCH v4 1/8] arm64: Do not enable IRQs for ct_user

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Message-ID: <20190611124542.GA29008@lakrids.cambridge.arm.com>
Date:   Tue, 11 Jun 2019 13:45:42 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Julien Thierry <julien.thierry@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, marc.zyngier@....com, yuzenghui@...wei.com,
        wanghaibin.wang@...wei.com, james.morse@....com,
        will.deacon@....com, catalin.marinas@....com, liwei391@...wei.com
Subject: Re: [PATCH v4 1/8] arm64: Do not enable IRQs for ct_user_exit

On Tue, Jun 11, 2019 at 10:38:06AM +0100, Julien Thierry wrote:
> For el0_dbg and el0_error, DAIF bits get explicitly cleared before
> calling ct_user_exit.
> 
> When context tracking is disabled, DAIF gets set (almost) immediately
> after. When context tracking is enabled, among the first things done
> is disabling IRQs.
> 
> What is actually needed is:
> - PSR.D = 0 so the system can be debugged (should be already the case)
> - PSR.A = 0 so async error can be handled during context tracking
> 
> Do not clear PSR.I in those two locations.
> 
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Reviewed-by: James Morse <james.morse@....com>
> Cc:Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/entry.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index cd0c7af..89ab6bd 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -870,7 +870,7 @@ el0_dbg:
>  	mov	x1, x25
>  	mov	x2, sp
>  	bl	do_debug_exception
> -	enable_daif
> +	enable_da_f
>  	ct_user_exit
>  	b	ret_to_user
>  el0_inv:
> @@ -922,7 +922,7 @@ el0_error_naked:
>  	enable_dbg
>  	mov	x0, sp
>  	bl	do_serror
> -	enable_daif
> +	enable_da_f
>  	ct_user_exit
>  	b	ret_to_user
>  ENDPROC(el0_error)
> --
> 1.9.1