Messages in this thread | | | Subject | Re: [PATCH v2 3/4] iommu/vt-d: Report page request faults for guest SVA | From | Lu Baolu <> | Date | Mon, 6 Jul 2020 15:37:50 +0800 |
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Hi Kevin,
On 2020/7/6 9:29, Tian, Kevin wrote: >> From: Lu Baolu <baolu.lu@linux.intel.com> >> Sent: Monday, July 6, 2020 8:26 AM >> >> A pasid might be bound to a page table from a VM guest via the iommu >> ops.sva_bind_gpasid. In this case, when a DMA page fault is detected >> on the physical IOMMU, we need to inject the page fault request into >> the guest. After the guest completes handling the page fault, a page >> response need to be sent back via the iommu ops.page_response(). >> >> This adds support to report a page request fault. Any external module >> which is interested in handling this fault should regiester a notifier >> callback. > > be specific on which notifier to be registered...
Sure.
> >> >> 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/svm.c | 99 ++++++++++++++++++++++++++++++++------- >> 1 file changed, 81 insertions(+), 18 deletions(-) >> >> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c >> index c23167877b2b..08c58c2b1a06 100644 >> --- a/drivers/iommu/intel/svm.c >> +++ b/drivers/iommu/intel/svm.c >> @@ -815,6 +815,57 @@ static void intel_svm_drain_prq(struct device *dev, >> int pasid) >> } >> } >> >> +static int prq_to_iommu_prot(struct page_req_dsc *req) >> +{ >> + int prot = 0; >> + >> + if (req->rd_req) >> + prot |= IOMMU_FAULT_PERM_READ; >> + if (req->wr_req) >> + prot |= IOMMU_FAULT_PERM_WRITE; >> + if (req->exe_req) >> + prot |= IOMMU_FAULT_PERM_EXEC; >> + if (req->pm_req) >> + prot |= IOMMU_FAULT_PERM_PRIV; >> + >> + return prot; >> +} >> + >> +static int >> +intel_svm_prq_report(struct device *dev, struct page_req_dsc *desc) >> +{ >> + struct iommu_fault_event event; >> + u8 bus, devfn; >> + >> + memset(&event, 0, sizeof(struct iommu_fault_event)); >> + bus = PCI_BUS_NUM(desc->rid); >> + devfn = desc->rid & 0xff; > > not required.
Yes. Will remove them.
> >> + >> + /* Fill in event data for device specific processing */ >> + event.fault.type = IOMMU_FAULT_PAGE_REQ; >> + event.fault.prm.addr = desc->addr; >> + event.fault.prm.pasid = desc->pasid; >> + event.fault.prm.grpid = desc->prg_index; >> + event.fault.prm.perm = prq_to_iommu_prot(desc); >> + >> + /* >> + * Set last page in group bit if private data is present, >> + * page response is required as it does for LPIG. >> + */ > > move to priv_data_present check?
Yes.
> >> + if (desc->lpig) >> + event.fault.prm.flags |= >> IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE; >> + if (desc->pasid_present) >> + event.fault.prm.flags |= >> IOMMU_FAULT_PAGE_REQUEST_PASID_VALID; >> + if (desc->priv_data_present) { >> + event.fault.prm.flags |= >> IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE; >> + event.fault.prm.flags |= >> IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA; >> + memcpy(event.fault.prm.private_data, desc->priv_data, >> + sizeof(desc->priv_data)); >> + } >> + >> + return iommu_report_device_fault(dev, &event); >> +} >> + >> static irqreturn_t prq_event_thread(int irq, void *d) >> { >> struct intel_iommu *iommu = d; >> @@ -828,7 +879,7 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & >> PRQ_RING_MASK; >> head = dmar_readq(iommu->reg + DMAR_PQH_REG) & >> PRQ_RING_MASK; >> while (head != tail) { >> - struct intel_svm_dev *sdev; >> + struct intel_svm_dev *sdev = NULL; > > move to outside of the loop, otherwise later check always hit "if (!sdev)"
Yes, good catch!
> >> struct vm_area_struct *vma; >> struct page_req_dsc *req; >> struct qi_desc resp; >> @@ -864,6 +915,20 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> } >> } >> >> + if (!sdev || sdev->sid != req->rid) { >> + struct intel_svm_dev *t; >> + >> + sdev = NULL; >> + rcu_read_lock(); >> + list_for_each_entry_rcu(t, &svm->devs, list) { >> + if (t->sid == req->rid) { >> + sdev = t; >> + break; >> + } >> + } >> + rcu_read_unlock(); >> + } >> + >> result = QI_RESP_INVALID; >> /* Since we're using init_mm.pgd directly, we should never >> take >> * any faults on kernel addresses. */ >> @@ -874,6 +939,17 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> if (!is_canonical_address(address)) >> goto bad_req; >> >> + /* >> + * If prq is to be handled outside iommu driver via receiver of >> + * the fault notifiers, we skip the page response here. >> + */ >> + if (svm->flags & SVM_FLAG_GUEST_MODE) { >> + if (sdev && !intel_svm_prq_report(sdev->dev, req)) >> + goto prq_advance; >> + else >> + goto bad_req; >> + } >> + >> /* If the mm is already defunct, don't handle faults. */ >> if (!mmget_not_zero(svm->mm)) >> goto bad_req; >> @@ -892,24 +968,10 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> goto invalid; >> >> result = QI_RESP_SUCCESS; >> - invalid: >> +invalid: >> mmap_read_unlock(svm->mm); >> mmput(svm->mm); >> - bad_req: >> - /* Accounting for major/minor faults? */ >> - rcu_read_lock(); >> - list_for_each_entry_rcu(sdev, &svm->devs, list) { >> - if (sdev->sid == req->rid) >> - break; >> - } >> - /* Other devices can go away, but the drivers are not >> permitted >> - * to unbind while any page faults might be in flight. So it's >> - * OK to drop the 'lock' here now we have it. */ > > should we keep and move this comment to earlier sdev lookup? and
I thought this comment explained why rcu_read_unlock() before the next checking. In the new lookup code, we don't need to check, hence I removed the comments.
> regarding to guest unbind, ae we preventing the fault owner (outside > of iommu driver) to unbind against in-flight fault request?
Yes. We always wait until all prq with the same pasid completes in gpasid_unbind().
> >> - rcu_read_unlock(); >> - >> - if (WARN_ON(&sdev->list == &svm->devs)) >> - sdev = NULL; > > similarly should we keep the WARN_ON check here?
Yes, agreed. We can keep a WARN_ON() here.
> >> - >> +bad_req: >> if (sdev && sdev->ops && sdev->ops->fault_cb) { >> int rwxp = (req->rd_req << 3) | (req->wr_req << 2) | >> (req->exe_req << 1) | (req->pm_req); >> @@ -920,7 +982,7 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> and these can be NULL. Do not use them below this point! >> */ >> sdev = NULL; >> svm = NULL; >> - no_pasid: >> +no_pasid: >> if (req->lpig || req->priv_data_present) { >> /* >> * Per VT-d spec. v3.0 ch7.7, system software must >> @@ -945,6 +1007,7 @@ static irqreturn_t prq_event_thread(int irq, void *d) >> resp.qw3 = 0; >> qi_submit_sync(iommu, &resp, 1, 0); >> } >> +prq_advance: >> head = (head + sizeof(*req)) & PRQ_RING_MASK; >> } >> >> -- >> 2.17.1 > > Thanks > Kevin >
Best regards, baolu
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