linux-kernel - Re: 32 bit qemu regression from v6.5 tip pull [6c480f222128 x86/alternative: Rewrite optimize

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Message-ID: <ZT/Lmj3xAdwvLE7R@windriver.com>
Date:   Mon, 30 Oct 2023 11:28:26 -0400
From:   Paul Gortmaker <paul.gortmaker@...driver.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Richard Purdie <richard.purdie@...uxfoundation.org>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: 32 bit qemu regression from v6.5 tip pull [6c480f222128
 x86/alternative: Rewrite optimize_nops() some]

[Re: 32 bit qemu regression from v6.5 tip pull [6c480f222128 x86/alternative: Rewrite optimize_nops() some]] On 30/10/2023 (Mon 12:44) Peter Zijlstra wrote:

> Thomas was looking at this and wondered if something like the below
> would help?

I tested this on a vanilla v6.5.7 baseline, for lack of a better choice
and got six failures in 136 boots - everything else unchanged - even the
shell instance that builds the kernel.

Paul.
--

> 
> ---
>  arch/x86/kernel/alternative.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 73be3931e4f0..fd44739828f7 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -1685,8 +1685,8 @@ void __init_or_module text_poke_early(void *addr, const void *opcode,
>  	} else {
>  		local_irq_save(flags);
>  		memcpy(addr, opcode, len);
> -		local_irq_restore(flags);
>  		sync_core();
> +		local_irq_restore(flags);
>  
>  		/*
>  		 * Could also do a CLFLUSH here to speed up CPU recovery; but

rp-qemu32-v6.5.7-tglx$while [ 1 ] ; do date ; ls -l1 qemurunner_log* | wc -l ; grep  -l   _common qemu_boot_log.2023* ;  sleep 5m ; done
Mon 30 Oct 2023 10:29:57 AM EDT
22
Mon 30 Oct 2023 10:34:57 AM EDT
32
qemu_boot_log.20231030103001
Mon 30 Oct 2023 10:39:57 AM EDT
46
qemu_boot_log.20231030103001
Mon 30 Oct 2023 10:44:57 AM EDT
60
qemu_boot_log.20231030103001
Mon 30 Oct 2023 10:49:57 AM EDT
70
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
Mon 30 Oct 2023 10:54:57 AM EDT
80
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
Mon 30 Oct 2023 10:59:57 AM EDT
89
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
qemu_boot_log.20231030105809
Mon 30 Oct 2023 11:04:57 AM EDT
99
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
qemu_boot_log.20231030105809
qemu_boot_log.20231030110019
Mon 30 Oct 2023 11:09:57 AM EDT
109
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
qemu_boot_log.20231030105809
qemu_boot_log.20231030110019
qemu_boot_log.20231030110615
Mon 30 Oct 2023 11:14:57 AM EDT
123
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
qemu_boot_log.20231030105809
qemu_boot_log.20231030110019
qemu_boot_log.20231030110615
Mon 30 Oct 2023 11:19:57 AM EDT
136
qemu_boot_log.20231030103001
qemu_boot_log.20231030104722
qemu_boot_log.20231030105036
qemu_boot_log.20231030105809
qemu_boot_log.20231030110019
qemu_boot_log.20231030110615
^C