Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED type of allocations

[Robin Murphy <robin.murphy@arm.com>]

On 2023-03-09 13:20, Robin Murphy wrote:
> On 2023-03-09 10:53, Nicolin Chen wrote:
>> Add domain allocation support for IOMMU_DOMAIN_NESTED type. This includes
>> the "finalise" part to log in the user space Stream Table Entry info.
>>
>> Co-developed-by: Eric Auger <eric.auger@redhat.com>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
>> ---
>>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 38 +++++++++++++++++++--
>>   1 file changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c 
>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 5ff74edfbd68..1f318b5e0921 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -2214,6 +2214,19 @@ static int arm_smmu_domain_finalise(struct 
>> iommu_domain *domain,
>>           return 0;
>>       }
>> +    if (domain->type == IOMMU_DOMAIN_NESTED) {
>> +        if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1) ||
>> +            !(smmu->features & ARM_SMMU_FEAT_TRANS_S2)) {
>> +            dev_dbg(smmu->dev, "does not implement two stages\n");
>> +            return -EINVAL;
>> +        }
>> +        smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
>> +        smmu_domain->s1_cfg.s1fmt = user_cfg->s1fmt;
>> +        smmu_domain->s1_cfg.s1cdmax = user_cfg->s1cdmax;
>> +        smmu_domain->s1_cfg.cdcfg.cdtab_dma = user_cfg->s1ctxptr;
>> +        return 0;
> 
> How's that going to work? If the caller's asked for something we can't 
> provide, returning something else and hoping it fails later is not 
> sensible, we should just fail right here. It's even more worrying if 
> there's a chance it *won't* fail later, and a guest ends up with 
> "nested" translation giving it full access to host PA space :/

Oops, apologies - in part thanks to the confusing indentation, I managed 
to miss the early return and misread this all being under the if 
condition for nesting not being supported. Sorry for the confusion :(

Thanks,
Robin.

>> +    }
>> +
>>       if (user_cfg_s2 && !(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
>>           return -EINVAL;
>>       if (user_cfg_s2)
>> @@ -2863,6 +2876,11 @@ static void arm_smmu_remove_dev_pasid(struct 
>> device *dev, ioasid_t pasid)
>>       arm_smmu_sva_remove_dev_pasid(domain, dev, pasid);
>>   }
>> +static const struct iommu_domain_ops arm_smmu_nested_domain_ops = {
>> +    .attach_dev        = arm_smmu_attach_dev,
>> +    .free            = arm_smmu_domain_free,
>> +};
>> +
>>   static struct iommu_domain *
>>   __arm_smmu_domain_alloc(unsigned type,
>>               struct arm_smmu_domain *s2,
>> @@ -2877,11 +2895,15 @@ __arm_smmu_domain_alloc(unsigned type,
>>           return arm_smmu_sva_domain_alloc();
>>       if (type != IOMMU_DOMAIN_UNMANAGED &&
>> +        type != IOMMU_DOMAIN_NESTED &&
>>           type != IOMMU_DOMAIN_DMA &&
>>           type != IOMMU_DOMAIN_DMA_FQ &&
>>           type != IOMMU_DOMAIN_IDENTITY)
>>           return NULL;
>> +    if (s2 && s2->stage != ARM_SMMU_DOMAIN_S2)
>> +        return NULL;
>> +
>>       /*
>>        * Allocate the domain and initialise some of its data structures.
>>        * We can't really finalise the domain unless a master is given.
>> @@ -2889,10 +2911,14 @@ __arm_smmu_domain_alloc(unsigned type,
>>       smmu_domain = kzalloc(sizeof(*smmu_domain), GFP_KERNEL);
>>       if (!smmu_domain)
>>           return NULL;
>> +    smmu_domain->s2 = s2;
>>       domain = &smmu_domain->domain;
>>       domain->type = type;
>> -    domain->ops = arm_smmu_ops.default_domain_ops;
>> +    if (s2)
>> +        domain->ops = &arm_smmu_nested_domain_ops;
>> +    else
>> +        domain->ops = arm_smmu_ops.default_domain_ops;
>>       mutex_init(&smmu_domain->init_mutex);
>>       INIT_LIST_HEAD(&smmu_domain->devices);
>> @@ -2923,8 +2949,16 @@ arm_smmu_domain_alloc_user(struct device *dev, 
>> struct iommu_domain *parent,
>>       const struct iommu_hwpt_arm_smmuv3 *user_cfg = user_data;
>>       struct arm_smmu_master *master = dev_iommu_priv_get(dev);
>>       unsigned type = IOMMU_DOMAIN_UNMANAGED;
>> +    struct arm_smmu_domain *s2 = NULL;
>> +
>> +    if (parent) {
>> +        if (parent->ops != arm_smmu_ops.default_domain_ops)
>> +            return NULL;
>> +        type = IOMMU_DOMAIN_NESTED;
>> +        s2 = to_smmu_domain(parent);
>> +    }
>> -    return __arm_smmu_domain_alloc(type, NULL, master, user_cfg);
>> +    return __arm_smmu_domain_alloc(type, s2, master, user_cfg);
>>   }
>>   static struct iommu_ops arm_smmu_ops = {
>