RE: [PATCH v3 4/4] iommu/vt-d: Add page response ops support

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Thursday, July 9, 2020 3:06 PM
> 
> After page requests are handled, software must respond to the device
> which raised the page request with the result. This is done through
> 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   | 100
> ++++++++++++++++++++++++++++++++++++
>  include/linux/intel-iommu.h |   3 ++
>  3 files changed, 104 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 4a6b6960fc32..98390a6d8113 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 d24e71bac8db..839d2af377b6 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -1082,3 +1082,103 @@ 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 = NULL;
> +	struct intel_svm *svm = NULL;
> +	struct intel_iommu *iommu;
> +	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;
> +
> +	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;
> +		}
> +
> +		/*
> +		 * For responses from userspace, need to make sure that the
> +		 * pasid has been bound to its mm.
> +		*/
> +		if (svm->flags & SVM_FLAG_GUEST_MODE) {
> +			struct mm_struct *mm;
> +
> +			mm = get_task_mm(current);
> +			if (!mm) {
> +				ret = -EINVAL;
> +				goto out;
> +			}
> +
> +			if (mm != svm->mm) {
> +				ret = -ENODEV;
> +				mmput(mm);
> +				goto out;
> +			}
> +
> +			mmput(mm);
> +		}
> +	} else {
> +		pr_err_ratelimited("Invalid page response: no pasid\n");
> +		ret = -EINVAL;
> +		goto out;

check pasid=0 first, then no need to indent so many lines above. 

> +	}
> +
> +	/*
> +	 * 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.
> +	 */

What is the behavior if system software doesn't follow the requirement?
en... maybe the question is really about whether the information in prm
comes from userspace or from internally-recorded info in iommu core.
The former cannot be trusted. The latter one is OK.

Thanks
Kevin

> +	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