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

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Message-ID: <35d68746-63e8-48f2-b4e3-045354a5934a@nvidia.com>
Date: Tue, 9 Dec 2025 17:59:13 +0000
From: Chaitanya Kulkarni <chaitanyak@...dia.com>
To: Robin Murphy <robin.murphy@....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 12/9/25 09:34, Robin Murphy wrote:
> 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.

sounds good, I'll send a patch and continue debugging the
problem further.

-ck