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Date: Fri, 10 Jul 2020 05:49:35 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
CC: Joerg Roedel <joro@...tes.org>,
Jacob Pan <jacob.jun.pan@...ux.intel.com>,
"Raj, Ashok" <ashok.raj@...el.com>,
"Liu, Yi L" <yi.l.liu@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 4/4] iommu/vt-d: Add page response ops support
> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Friday, July 10, 2020 1:37 PM
>
> Hi Kevin,
>
> On 2020/7/10 10:42, Tian, Kevin wrote:
> >> From: Lu Baolu <baolu.lu@...ux.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@...ux.intel.com>
> >> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> >> Co-developed-by: Liu Yi L <yi.l.liu@...el.com>
> >> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
> >> Signed-off-by: Lu Baolu <baolu.lu@...ux.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.
>
> Yes.
>
> >
> >> + }
> >> +
> >> + /*
> >> + * 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.
>
> We require a page response when reporting such event. The upper layer
> (IOMMU core or VFIO) will be implemented with a timer, if userspace
> doesn't respond in time, the timer will get expired and a FAILURE
> response will be sent to device.
Yes, timer helps when userspace doesn't respond. Then I'm fine with
this patch.
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
btw when you say IOMMU core or VFIO, does it mean the timer mechanism
is not implemented yet?
Thanks
Kevin
>
> Best regards,
> baolu
>
> >
> > 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
> >
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