linux-kernel - Re: [PATCH V5 08/11] riscv: Support HAVE_IRQ_EXIT_ON_IRQ

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Message-ID: <afa17bdd-2d11-4015-6e2a-7a39db931d09@huawei.com>
Date:   Wed, 21 Sep 2022 16:34:52 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <guoren@...nel.org>, <arnd@...db.de>, <palmer@...osinc.com>,
        <tglx@...utronix.de>, <peterz@...radead.org>, <luto@...nel.org>,
        <conor.dooley@...rochip.com>, <heiko@...ech.de>,
        <jszhang@...nel.org>, <lazyparser@...il.com>, <falcon@...ylab.org>,
        <chenhuacai@...nel.org>, <apatel@...tanamicro.com>,
        <atishp@...shpatra.org>, <palmer@...belt.com>,
        <paul.walmsley@...ive.com>, <mark.rutland@....com>,
        <zouyipeng@...wei.com>, <bigeasy@...utronix.de>,
        <David.Laight@...lab.com>
CC:     <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V5 08/11] riscv: Support HAVE_IRQ_EXIT_ON_IRQ_STACK

Hi,

On 2022/9/18 23:52, guoren@...nel.org wrote:
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 5f49517cd3a2..426529b84db0 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -332,6 +332,33 @@ ENTRY(ret_from_kernel_thread)
>   	tail syscall_exit_to_user_mode
>   ENDPROC(ret_from_kernel_thread)
>   
> +#ifdef CONFIG_IRQ_STACKS
> +ENTRY(call_on_stack)
> +	/* Create a frame record to save our ra and fp */
> +	addi	sp, sp, -RISCV_SZPTR
> +	REG_S	ra, (sp)
> +	addi	sp, sp, -RISCV_SZPTR
> +	REG_S	fp, (sp)
> +
> +	/* Save sp in fp */
> +	move	fp, sp
> +
> +	/* Move to the new stack and call the function there */
> +	li	a3, IRQ_STACK_SIZE
> +	add	sp, a1, a3
> +	jalr	a2
> +
> +	/*
> +	 * Restore sp from prev fp, and fp, ra from the frame
> +	 */
> +	move	sp, fp
> +	REG_L	fp, (sp)
> +	addi	sp, sp, RISCV_SZPTR
> +	REG_L	ra, (sp)
> +	addi	sp, sp, RISCV_SZPTR
> +	ret
> +ENDPROC(call_on_stack)
> +#endif

Seems my compiler (riscv64-linux-gnu-gcc 8.4.0, cross compiling from 
x86) cannot recognize the register `fp`.

After I changed it to `s0` this can pass compiling.


Seems there is nowhere else using `fp`, can this just using `s0` instead?

Best,

Chen