linux-kernel - Re: [PATCH] riscv: kexec: Cleanup riscv_kexec

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Date:   Thu, 31 Aug 2023 09:38:38 +0200
From:   Andreas Schwab <schwab@...e.de>
To:     Song Shuai <songshuaishuai@...ylab.org>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, mick@....forth.gr, alex@...ti.fr,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: kexec: Cleanup riscv_kexec_relocate

On Aug 31 2023, Song Shuai wrote:

> Hi, Andreas:
>
> 在 2023/8/30 15:24, Andreas Schwab 写道:
>> On Aug 30 2023, Song Shuai wrote:
>> 
>>> @@ -52,21 +42,27 @@ SYM_CODE_START(riscv_kexec_relocate)
>>>   	 * the start of the loop below so that we jump there in
>>>   	 * any case.
>>>   	 */
>>> -	la	s8, 1f
>>> -	sub	s8, s8, s7
>>> -	csrw	CSR_STVEC, s8
>>> +	la	s6, 1f
>>> +	sub	s6, s6, s4
>>> +	csrw	CSR_STVEC, s6
>>> +
>>> +	/*
>>> +	 * With C-extension, here we get 42 Bytes and the next
>>> +	 * .align directive would pad zeros here up to 44 Bytes.
>>> +	 * So manually put a nop here to avoid zeros padding.
>>> +	*/
>>> +	nop
>>>     	/* Process entries in a loop */
>>>   .align 2
>> While you are at it, I'd suggest being explicit about .palign
>> vs. .balign.
>> 
> How about this commemt:

My suggestion is to change .align 2 in the last line to .palign 2 as
part of the cleanup.  The meaning of .align is target dependent, and
someone not familiar with RISC-V may misinterpret it.

-- 
Andreas Schwab, SUSE Labs, schwab@...e.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."