linux-kernel - Re: [PATCH v2] x86/ioremap: Use is_ioremap

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Message-ID: <87wmkjnqi4.ffs@tglx>
Date: Wed, 14 Aug 2024 16:11:31 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Christoph Hellwig <hch@...radead.org>, Alistair Popple <apopple@...dia.com>
Cc: Christoph Hellwig <hch@...radead.org>, Max Ramanouski
 <max8rr8@...il.com>, x86@...nel.org, dave.hansen@...ux.intel.com,
 luto@...nel.org, peterz@...radead.org, linux-kernel@...r.kernel.org,
 jniethe@...dia.com, jhubbard@...dia.com, linux-mm@...ck.org
Subject: Re: [PATCH v2] x86/ioremap: Use is_ioremap_addr() in iounmap()

On Wed, Aug 14 2024 at 05:16, Christoph Hellwig wrote:
> On Wed, Aug 14, 2024 at 10:08:23PM +1000, Alistair Popple wrote:
>> I would tend to agree and had the same thought when we found this. At
>> least some kind of message (WARN_ON, WARN_ON_ONCE, printk, etc) would
>> have made the issue we were debugging much more obvious. FWIW I have
>> tested running with a WARN_ON() there and it never fired except in the
>> bug scenario.
>
> Various architectures had either an early ioremap variant that got
> silently ignored here, or magic carveout that don't get remapped at all.
> None of this should currently apply to x86, though.

So I'm inclined to have:

       if (WARN_ON_ONCE(is_ioremap_addr(addr)))
       		return;

in the x86 variant then.

Thanks,

        tglx