linux-kernel - Re: WARNING: drivers/iommu/io-pgtable-arm.c:639

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Message-ID: <3451a93a-e4d5-4017-b4e3-e58fae3751f8@arm.com>
Date: Tue, 9 Dec 2025 17:34:10 +0000
From: Robin Murphy <robin.murphy@....com>
To: Chaitanya Kulkarni <chaitanyak@...dia.com>
Cc: Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
 Will Deacon <will@...nel.org>, Carlos Maiolino <cem@...nel.org>,
 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
 "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
 "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
 Sebastian Ott <sebott@...hat.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: WARNING: drivers/iommu/io-pgtable-arm.c:639

On 2025-12-09 5:29 pm, Chaitanya Kulkarni wrote:
> On 12/9/25 03:50, Robin Murphy wrote:
>> On 2025-12-09 11:43 am, Sebastian Ott wrote:
>>> Hi,
>>>
>>> got the following warning after a kernel update on Thurstday, leading
>>> to a
>>> panic and fs corruption. I didn't capture the first warning but I'm
>>> pretty
>>> sure it was the same. It's reproducible but I didn't bisect since it
>>> borked my fs. The only hint I can give is that v6.18 worked. Is this a
>>> known issue? Anything I should try?
>>
>> nvme_unmap_data() is attempting to unmap an IOVA that was never
>> mapped, or has already been unmapped by someone else. That's a usage bug.
>>
>> Thanks,
>> Robin.
> 
> Ankit A. also reported this.
> 
> Apart from unmapping, by any chance do we need this ?
> 
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index e6626004b323..05d63fe92e43 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -637,7 +637,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
>    	pte = READ_ONCE(*ptep);
>    	if (!pte) {
>    		WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN));
> -		return -ENOENT;
> +		return 0;
>    	}
>    
>    	/* If the size matches this level, we're in the right place */

Oh, indeed - I also happened to notice that the other week and was 
intending to write up a fix, but apparently I completely forgot about it 
already :(

If you're happy to write that up and send a proper patch, please do - 
otherwise I'll try to get it done before I forget again...

Thanks,
Robin.