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

Tian, Kevin
2020-07-06T01:47:18Z

> 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.

> 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?

> +
> + 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?

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)?

Thanks
Kevin

> +
> + /*
> + * 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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