Re: [PATCH v2 18/24] iommu: Express DMA strictness via the domain type

[Lu Baolu <baolu.lu@linux.intel.com>]

On 7/29/21 5:36 PM, Robin Murphy wrote:
> On 2021-07-29 08:13, Lu Baolu wrote:
>> Hi Robin,
>>
>> On 7/28/21 11:58 PM, Robin Murphy wrote:
>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>> index 982545234cf3..eecb5657de69 100644
>>> --- a/drivers/iommu/iommu.c
>>> +++ b/drivers/iommu/iommu.c
>>> @@ -136,6 +136,9 @@ static int __init iommu_subsys_init(void)
>>>           }
>>>       }
>>> +    if (!iommu_default_passthrough() && !iommu_dma_strict)
>>> +        iommu_def_domain_type = IOMMU_DOMAIN_DMA_FQ;
>>
>> iommu_dma_strict could be changed later by the vendor iommu driver via
>> iommu_set_dma_strict(). This seems not to be the right place to set
>> iommu_def_domain_type.
> 
> Ah yes, good catch once again, thanks!
> 
> I think this *is* the right place to initially set it to honour the 
> command-line option, since that matches what we do for passthrough. 
> However also like passthrough we'll need to keep things in sync if it's 
> updated later, like this:
> 
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 87d7b299436e..593d4555bc57 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -359,6 +359,8 @@ early_param("iommu.strict", iommu_dma_setup);
>   void iommu_set_dma_strict(void)
>   {
>          iommu_dma_strict = true;
> +       if (iommu_def_domain_type == IOMMU_DOMAIN_DMA_FQ)
> +               iommu_def_domain_type = IOMMU_DOMAIN_DMA;
>   }
> 
>   static ssize_t iommu_group_attr_show(struct kobject *kobj,
> 
> 
> Does that seem reasonable? I'm not sure there's any cleaner way to do it 
> since we don't want to inadvertently clobber the default type if the 
> user has given us something funky like "intel_iommu=strict 
> iommu.passthrough=1".
> 
> Cheers,
> Robin.
> 
>>
>>> +
>>>       pr_info("Default domain type: %s %s\n",
>>>           iommu_domain_type_str(iommu_def_domain_type),
>>>           (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>>
>> Best regards,
>> baolu

With above fixed,

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu