linux-kernel - Re: [PATCH] mm/ioremap: Use WARN_ONCE instead of printk() + WARN_ON

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Message-ID: <5DBB03B0.5060003@huawei.com>
Date:   Thu, 31 Oct 2019 23:54:24 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <peterz@...radead.org>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <dave.hansen@...ux.intel.com>, <hpa@...or.com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/ioremap: Use WARN_ONCE instead of printk() + WARN_ON_ONCE()

On 2019/10/31 23:49, Borislav Petkov wrote:
> On Thu, Oct 31, 2019 at 07:54:09PM +0800, zhong jiang wrote:
>> Look at this again, It should not works. Because that will change the logical.
>> if phys_addr_valid is false, we should drop out in time.
> That you can do too:
>
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index a39dcdb5ae34..13f44cc064af 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -171,12 +171,10 @@ __ioremap_caller(resource_size_t phys_addr, unsigned long size,
>  	if (!size || last_addr < phys_addr)
>  		return NULL;
>  
> -	if (!phys_addr_valid(phys_addr)) {
> -		printk(KERN_WARNING "ioremap: invalid physical address %llx\n",
> -		       (unsigned long long)phys_addr);
> -		WARN_ON_ONCE(1);
> +	if (WARN_ONCE(!phys_addr_valid(phys_addr),
> +	    "ioremap: invalid physical address %llx\n",
> +	    (unsigned long long)phys_addr))
>  		return NULL;
> -	}
>  
Yep,  WARN_ONCE alway return true in that case.

Thanks,
zhong jiang
>  	__ioremap_check_mem(phys_addr, size, &io_desc);
>  
> ---
>
> I'm not sure whether we care about printing every invalid address, as
> Joe points out. Maybe we do... *shrug*
>