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

[Robin Murphy]

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.