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SubjectRe: [PATCH v9 1/4] iommu: Move def_domain type check for untrusted device into core
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Hi Will,

On 2020/11/23 20:04, Will Deacon wrote:
> On Sat, Nov 21, 2020 at 09:56:17PM +0800, Lu Baolu wrote:
>> So that the vendor iommu drivers are no more required to provide the
>> def_domain_type callback to always isolate the untrusted devices.
>>
>> Link: https://lore.kernel.org/linux-iommu/243ce89c33fe4b9da4c56ba35acebf81@huawei.com/
>> Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/intel/iommu.c | 7 -------
>> drivers/iommu/iommu.c | 21 ++++++++++++++-------
>> 2 files changed, 14 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index af3abd285214..6711f78141a4 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -2916,13 +2916,6 @@ static int device_def_domain_type(struct device *dev)
>> if (dev_is_pci(dev)) {
>> struct pci_dev *pdev = to_pci_dev(dev);
>>
>> - /*
>> - * Prevent any device marked as untrusted from getting
>> - * placed into the statically identity mapping domain.
>> - */
>> - if (pdev->untrusted)
>> - return IOMMU_DOMAIN_DMA;
>> -
>> if ((iommu_identity_mapping & IDENTMAP_AZALIA) && IS_AZALIA(pdev))
>> return IOMMU_DOMAIN_IDENTITY;
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 88b0c9192d8c..3256784c0358 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1457,13 +1457,23 @@ struct iommu_group *fsl_mc_device_group(struct device *dev)
>> }
>> EXPORT_SYMBOL_GPL(fsl_mc_device_group);
>>
>> -static int iommu_get_def_domain_type(struct device *dev)
>> +/* Get the mandatary def_domain type for device. Otherwise, return 0. */
>> +static int iommu_get_mandatory_def_domain_type(struct device *dev)
>> {
>> const struct iommu_ops *ops = dev->bus->iommu_ops;
>> - unsigned int type = 0;
>> +
>> + if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
>> + return IOMMU_DOMAIN_DMA;
>>
>> if (ops->def_domain_type)
>> - type = ops->def_domain_type(dev);
>> + return ops->def_domain_type(dev);
>> +
>> + return 0;
>> +}
>> +
>> +static int iommu_get_def_domain_type(struct device *dev)
>> +{
>> + int type = iommu_get_mandatory_def_domain_type(dev);
>>
>> return (type == 0) ? iommu_def_domain_type : type;
>> }
>> @@ -1645,13 +1655,10 @@ struct __group_domain_type {
>>
>> static int probe_get_default_domain_type(struct device *dev, void *data)
>> {
>> - const struct iommu_ops *ops = dev->bus->iommu_ops;
>> struct __group_domain_type *gtype = data;
>> unsigned int type = 0;
>>
>> - if (ops->def_domain_type)
>> - type = ops->def_domain_type(dev);
>> -
>> + type = iommu_get_mandatory_def_domain_type(dev);
>
> afaict, this code is only called from probe_alloc_default_domain(), which
> has:
>
> /* Ask for default domain requirements of all devices in the group */
> __iommu_group_for_each_dev(group, &gtype,
> probe_get_default_domain_type);
>
> if (!gtype.type)
> gtype.type = iommu_def_domain_type;
>
> so is there actually a need to introduce the new
> iommu_get_mandatory_def_domain_type() function, given that a type of 0
> always ends up resolving to the default domain type?

Another consumer of this helper is in the next patch:

+ dev_def_dom = iommu_get_mandatory_def_domain_type(dev);
+
+ /* Check if user requested domain is supported by the device or not */
+ if (!type) {
+ /*
+ * If the user hasn't requested any specific type of domain and
+ * if the device supports both the domains, then default to the
+ * domain the device was booted with
+ */
+ type = iommu_get_def_domain_type(dev);
+ } else if (dev_def_dom && type != dev_def_dom) {
+ dev_err_ratelimited(prev_dev, "Device cannot be in %s domain\n",
+ iommu_domain_type_str(type));
+ ret = -EINVAL;
+ goto out;
+ }

I also added the untrusted device check in
iommu_get_mandatory_def_domain_type(), so that we don't need to care
about this in multiple places.

Best regards,
baolu

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