This is required.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
---
 drivers/iommu/apple-dart.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
index 9c74a95eb7e819e94ab2fb47ed0d411a1eba8bf7..9c6f780dc7220096ed6bba692fa1a4bd859b0d61 100644
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -941,6 +941,8 @@ static int apple_dart_def_domain_type(struct device *dev)
 		return IOMMU_DOMAIN_IDENTITY;
 	if (!cfg->stream_maps[0].dart->supports_bypass)
 		return IOMMU_DOMAIN_DMA;
+	if (cfg->stream_maps[0].dart->locked)
+		return IOMMU_DOMAIN_DMA;
 
 	return 0;
 }

-- 
2.48.1

On 2025-02-10 7:39 pm, Alyssa Rosenzweig wrote:
> This is required.

Now that we can, I'd really rather do this properly and not offer an 
identity domain in the first place when it's not available.

Thanks,
Robin.

> Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> ---
>   drivers/iommu/apple-dart.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index 9c74a95eb7e819e94ab2fb47ed0d411a1eba8bf7..9c6f780dc7220096ed6bba692fa1a4bd859b0d61 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -941,6 +941,8 @@ static int apple_dart_def_domain_type(struct device *dev)
>   		return IOMMU_DOMAIN_IDENTITY;
>   	if (!cfg->stream_maps[0].dart->supports_bypass)
>   		return IOMMU_DOMAIN_DMA;
> +	if (cfg->stream_maps[0].dart->locked)
> +		return IOMMU_DOMAIN_DMA;
>   
>   	return 0;
>   }
>

Hi Robin,

> > This is required.
> 
> Now that we can, I'd really rather do this properly and not offer an
> identity domain in the first place when it's not available.

I'm reading through iommu.c but I don't see a way to avoid offering an
identity domain without the DMA override here, just reading through the
logic of iommu_get_default_domain_type. Could you point me to what you
have in mind?

Thanks,
Alyssa

> > --- a/drivers/iommu/apple-dart.c
> > +++ b/drivers/iommu/apple-dart.c
> > @@ -941,6 +941,8 @@ static int apple_dart_def_domain_type(struct device *dev)
> >   		return IOMMU_DOMAIN_IDENTITY;
> >   	if (!cfg->stream_maps[0].dart->supports_bypass)
> >   		return IOMMU_DOMAIN_DMA;
> > +	if (cfg->stream_maps[0].dart->locked)
> > +		return IOMMU_DOMAIN_DMA;
> >   	return 0;
> >   }
> > 
>

On 2025-02-11 6:40 pm, Alyssa Rosenzweig wrote:
> Hi Robin,
> 
>>> This is required.
>>
>> Now that we can, I'd really rather do this properly and not offer an
>> identity domain in the first place when it's not available.
> 
> I'm reading through iommu.c but I don't see a way to avoid offering an
> identity domain without the DMA override here, just reading through the
> logic of iommu_get_default_domain_type. Could you point me to what you
> have in mind?

Since we finished cleaning up the domain allocation paths, it's finally 
safe to have per-instance ops, so you can mix and match some with an 
identity domain and some without, as s390 will be doing[1].

Cheers,
Robin.

[1] 
https://lore.kernel.org/linux-iommu/20250207205335.473946-5-mjrosato@linux.ibm.com/

> Thanks,
> Alyssa
> 
>>> --- a/drivers/iommu/apple-dart.c
>>> +++ b/drivers/iommu/apple-dart.c
>>> @@ -941,6 +941,8 @@ static int apple_dart_def_domain_type(struct device *dev)
>>>    		return IOMMU_DOMAIN_IDENTITY;
>>>    	if (!cfg->stream_maps[0].dart->supports_bypass)
>>>    		return IOMMU_DOMAIN_DMA;
>>> +	if (cfg->stream_maps[0].dart->locked)
>>> +		return IOMMU_DOMAIN_DMA;
>>>    	return 0;
>>>    }
>>>
>>