Subject: Re: [PATCH 6/8] iommu/dart: Move the blocked domain support to a global static

From: Janne Grunau <[email-masked]>
Date: Tue, 26 Sep 2023 21:05:08 +0200

Hej,

On Fri, Sep 22, 2023 at 02:07:57PM -0300, Jason Gunthorpe wrote:
> Move to the new static global for blocked domains. Move the blocked
> specific code to apple_dart_attach_dev_blocked().
> 
> Signed-off-by: Jason Gunthorpe <[email-masked]>
> ---
>  drivers/iommu/apple-dart.c | 36 ++++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index 424f779ccc34df..376f4c5461e8f7 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -675,10 +675,6 @@ static int apple_dart_attach_dev(struct iommu_domain *domain,
>  		for_each_stream_map(i, cfg, stream_map)
>  			apple_dart_setup_translation(dart_domain, stream_map);
>  		break;
> -	case IOMMU_DOMAIN_BLOCKED:
> -		for_each_stream_map(i, cfg, stream_map)
> -			apple_dart_hw_disable_dma(stream_map);
> -		break;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -710,6 +706,30 @@ static struct iommu_domain apple_dart_identity_domain = {
>  	.ops = &apple_dart_identity_ops,
>  };
>  
> +static int apple_dart_attach_dev_blocked(struct iommu_domain *domain,
> +					 struct device *dev)
> +{
> +	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	struct apple_dart_stream_map *stream_map;
> +	int i;
> +
> +	if (cfg->stream_maps[0].dart->force_bypass)
> +		return -EINVAL;

unrelated to this change as this keeps the current behavior but I think
force_bypass should not override IOMMU_DOMAIN_BLOCKED. It is set if the
CPU page size is smaller than dart's page size. Obviously dart can't
translate in that situation but it should be still possible to block it
completely.

How do we manage this? I can write a patch either to the current state
or based on this series.

> +
> +	for_each_stream_map(i, cfg, stream_map)
> +		apple_dart_hw_disable_dma(stream_map);
> +	return 0;
> +}
> +
> +static const struct iommu_domain_ops apple_dart_blocked_ops = {
> +	.attach_dev = apple_dart_attach_dev_blocked,
> +};
> +
> +static struct iommu_domain apple_dart_blocked_domain = {
> +	.type = IOMMU_DOMAIN_BLOCKED,
> +	.ops = &apple_dart_blocked_ops,
> +};
> +
>  static struct iommu_device *apple_dart_probe_device(struct device *dev)
>  {
>  	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
> @@ -739,8 +759,7 @@ static struct iommu_domain *apple_dart_domain_alloc(unsigned int type)
>  {
>  	struct apple_dart_domain *dart_domain;
>  
> -	if (type != IOMMU_DOMAIN_DMA && type != IOMMU_DOMAIN_UNMANAGED &&
> -	    type != IOMMU_DOMAIN_BLOCKED)
> +	if (type != IOMMU_DOMAIN_DMA && type != IOMMU_DOMAIN_UNMANAGED)
>  		return NULL;
>  
>  	dart_domain = kzalloc(sizeof(*dart_domain), GFP_KERNEL);
> @@ -749,10 +768,6 @@ static struct iommu_domain *apple_dart_domain_alloc(unsigned int type)
>  
>  	mutex_init(&dart_domain->init_lock);
>  
> -	/* no need to allocate pgtbl_ops or do any other finalization steps */
> -	if (type == IOMMU_DOMAIN_BLOCKED)
> -		dart_domain->finalized = true;
> -
>  	return &dart_domain->domain;
>  }
>  
> @@ -966,6 +981,7 @@ static void apple_dart_get_resv_regions(struct device *dev,
>  
>  static const struct iommu_ops apple_dart_iommu_ops = {
>  	.identity_domain = &apple_dart_identity_domain,
> +	.blocked_domain = &apple_dart_blocked_domain,
>  	.domain_alloc = apple_dart_domain_alloc,
>  	.probe_device = apple_dart_probe_device,
>  	.release_device = apple_dart_release_device,
> -- 
> 2.42.0

Reviewed-by: Janne Grunau <[email-masked]>

best regards
Janne

ps: I sent the reply to [Patch 4/8] accidentally with an incorrect from
address but the correct Reviewed-by:. I can resend if necessary.