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SubjectRe: [PATCH 2/2] iommu/vt-d: Replace intel SVM APIs with generic SVA APIs
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On 2020/3/24 7:01, Raj, Ashok wrote:
> Hi Jean
>
> On Fri, Mar 20, 2020 at 10:29:55AM +0100, Jean-Philippe Brucker wrote:
>>> +#define to_intel_svm_dev(handle) container_of(handle, struct intel_svm_dev, sva)
>>> +struct iommu_sva *
>>> +intel_svm_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
>>> +{
>>> + struct iommu_sva *sva = ERR_PTR(-EINVAL);
>>> + struct intel_svm_dev *sdev = NULL;
>>> + int flags = 0;
>>> + int ret;
>>> +
>>> + /*
>>> + * TODO: Consolidate with generic iommu-sva bind after it is merged.
>>> + * It will require shared SVM data structures, i.e. combine io_mm
>>> + * and intel_svm etc.
>>> + */
>>> + if (drvdata)
>>> + flags = *(int *)drvdata;
>>
>> drvdata is more for storing device driver contexts that can be passed to
>> iommu_sva_ops, but I get that this is temporary.
>>
>> As usual I'm dreading supervisor mode making it into the common API. What
>> are your plans regarding SUPERVISOR_MODE and PRIVATE_PASID flags? The
>> previous discussion on the subject [1] had me hoping that you could
>> replace supervisor mode with normal mappings (auxiliary domains?)
>> I'm less worried about PRIVATE_PASID, it would just add complexity into
>
> We don't seem to have an immediate need for PRIVATE_PASID. There are some talks
> about potential usages, but nothing concrete. I think it might be good to
> get rid of it now and add when we really need.
>
> For SUPERVISOR_MODE, the idea is to have aux domain. Baolu is working on
> something to replace. Certainly the entire kernel address is opening up
> the whole kimono.. so we are looking at dynamically creating mappings on demand.
> It might take some of the benefits of SVA in general with no need to create
> mappings, but for security somebody has to pay the price :-)

My thought is to reuse below aux-domain API.

int iommu_aux_attach_device(struct iommu_domain *domain,
struct device *dev)

Currently, it asks the vendor iommu driver to allocate a PASID and bind
the domain with it. We can change it to allow the caller to pass in an
existing supervisor PASID.

int iommu_aux_attach_device(struct iommu_domain *domain,
struct device *dev,
int *pasid)

In the vendor iommu driver, if (*pasid == INVALID_IOASID), it will
allocate a pasid (the same as current behavior); otherwise, attach
the domain with the pass-in pasid.

Best regards,
baolu

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