Re: [PATCH v2 4/4] iommu/vt-d: Add page response ops support

Lu Baolu
2020-07-09T00:37:34Z

Hi Kevin,

On 7/6/20 9:47 AM, Tian, Kevin wrote:
>> From: Lu Baolu
>> Sent: Monday, July 6, 2020 8:26 AM
>>
>> After a page request is handled, software must response the device which
>> raised the page request with the handling result. This is done through
>
> 'response' is a noun.

Yes.

>
>> the iommu ops.page_response if the request was reported to outside of
>> vendor iommu driver through iommu_report_device_fault(). This adds the
>> VT-d implementation of page_response ops.
>>
>> Co-developed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Co-developed-by: Liu Yi L <yi.l.liu@intel.com>
>> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/intel/iommu.c | 1 +
>> drivers/iommu/intel/svm.c | 74
>> +++++++++++++++++++++++++++++++++++++
>> include/linux/intel-iommu.h | 3 ++
>> 3 files changed, 78 insertions(+)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index de17952ed133..7eb29167e8f9 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -6057,6 +6057,7 @@ const struct iommu_ops intel_iommu_ops = {
>> .sva_bind = intel_svm_bind,
>> .sva_unbind = intel_svm_unbind,
>> .sva_get_pasid = intel_svm_get_pasid,
>> + .page_response = intel_svm_page_response,
>> #endif
>> };
>>
>> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
>> index 08c58c2b1a06..1c7d8a9ea124 100644
>> --- a/drivers/iommu/intel/svm.c
>> +++ b/drivers/iommu/intel/svm.c
>> @@ -1078,3 +1078,77 @@ int intel_svm_get_pasid(struct iommu_sva *sva)
>>
>> return pasid;
>> }
>> +
>> +int intel_svm_page_response(struct device *dev,
>> + struct iommu_fault_event *evt,
>> + struct iommu_page_response *msg)
>> +{
>> + struct iommu_fault_page_request *prm;
>> + struct intel_svm_dev *sdev;
>> + struct intel_iommu *iommu;
>> + struct intel_svm *svm;
>> + bool private_present;
>> + bool pasid_present;
>> + bool last_page;
>> + u8 bus, devfn;
>> + int ret = 0;
>> + u16 sid;
>> +
>> + if (!dev || !dev_is_pci(dev))
>> + return -ENODEV;
>
> but we didn't do same check when reporting fault?

For now, we only support PCI devices, so I will add this check in report
as well.

>
>> +
>> + iommu = device_to_iommu(dev, &bus, &devfn);
>> + if (!iommu)
>> + return -ENODEV;
>> +
>> + if (!msg || !evt)
>> + return -EINVAL;
>> +
>> + mutex_lock(&pasid_mutex);
>> +
>> + prm = &evt->fault.prm;
>> + sid = PCI_DEVID(bus, devfn);
>> + pasid_present = prm->flags &
>> IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
>> + private_present = prm->flags &
>> IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA;
>> + last_page = prm->flags &
>> IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
>> +
>> + if (pasid_present) {
>> + if (prm->pasid == 0 || prm->pasid >= PASID_MAX) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> + ret = pasid_to_svm_sdev(dev, prm->pasid, &svm, &sdev);
>> + if (ret || !sdev) {
>> + ret = -ENODEV;
>> + goto out;
>> + }
>> + }
>
> what about pasid_present==0? Do we support recoverable fault now
> with this patch?

For now, we don't support reporting a prq without pasid to outside.
prq_event_thread() handles such requests explicitly. I will add a
check in response ops.

>
> and who guarantees that the external fault handler (e.g. guest)
> cannot do bad thing with this interface, e.g. by specifying a PASID
> belonging to other guests (when Scalable IOV is enabled)?

I will check below if the response is from user space.

(svm->mm == get_task_mm(current))

>
> Thanks
> Kevin

Best regards,
baolu

>> +
>> + /*
>> + * Per VT-d spec. v3.0 ch7.7, system software must respond
>> + * with page group response if private data is present (PDP)
>> + * or last page in group (LPIG) bit is set. This is an
>> + * additional VT-d requirement beyond PCI ATS spec.
>> + */
>> + if (last_page || private_present) {
>> + struct qi_desc desc;
>> +
>> + desc.qw0 = QI_PGRP_PASID(prm->pasid) | QI_PGRP_DID(sid)
>> |
>> + QI_PGRP_PASID_P(pasid_present) |
>> + QI_PGRP_PDP(private_present) |
>> + QI_PGRP_RESP_CODE(msg->code) |
>> + QI_PGRP_RESP_TYPE;
>> + desc.qw1 = QI_PGRP_IDX(prm->grpid) |
>> QI_PGRP_LPIG(last_page);
>> + desc.qw2 = 0;
>> + desc.qw3 = 0;
>> + if (private_present)
>> + memcpy(&desc.qw2, prm->private_data,
>> + sizeof(prm->private_data));
>> +
>> + qi_submit_sync(iommu, &desc, 1, 0);
>> + }
>> +out:
>> + mutex_unlock(&pasid_mutex);
>> + return ret;
>> +}
>> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
>> index fc2cfc3db6e1..bf6009a344f5 100644
>> --- a/include/linux/intel-iommu.h
>> +++ b/include/linux/intel-iommu.h
>> @@ -741,6 +741,9 @@ struct iommu_sva *intel_svm_bind(struct device
>> *dev, struct mm_struct *mm,
>> void *drvdata);
>> void intel_svm_unbind(struct iommu_sva *handle);
>> int intel_svm_get_pasid(struct iommu_sva *handle);
>> +int intel_svm_page_response(struct device *dev, struct iommu_fault_event
>> *evt,
>> + struct iommu_page_response *msg);
>> +
>> struct svm_dev_ops;
>>
>> struct intel_svm_dev {
>> --
>> 2.17.1
>>
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