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Date: Fri, 10 Jul 2020 13:25:33 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Cc: baolu.lu@...ux.intel.com, 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 3/4] iommu/vt-d: Report page request faults for guest
SVA
Hi Kevin,
On 2020/7/10 10:24, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Thursday, July 9, 2020 3:06 PM
>>
>> 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
>> with iommu_register_device_fault_handler().
>>
>> 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/svm.c | 103 +++++++++++++++++++++++++++++++-------
>> 1 file changed, 85 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
>> index c23167877b2b..d24e71bac8db 100644
>> --- a/drivers/iommu/intel/svm.c
>> +++ b/drivers/iommu/intel/svm.c
>> @@ -815,8 +815,63 @@ 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;
>> +
>> + /* Fill in event data for device specific processing */
>> + memset(&event, 0, sizeof(struct iommu_fault_event));
>> + 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);
>> +
>> + if (!dev || !dev_is_pci(dev))
>> + return -ENODEV;
>
> move the check before memset.
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;
>> + event.fault.prm.flags |=
>> IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID;
>> + }
>
> if pasid is not present, should we return error directly instead of
> submitting the req and let iommu core to figure out? I don't have
This has been done in prq_event_thread(), so I don't need to check it
again here.
> a strong preference, thus:
>
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Thanks a lot for your time.
Best regards,
baolu
>
>> + if (desc->priv_data_present) {
>> + /*
>> + * Set last page in group bit if private data is present,
>> + * page response is required as it does for LPIG.
>> + * iommu_report_device_fault() doesn't understand this
>> vendor
>> + * specific requirement thus we set last_page as a
>> workaround.
>> + */
>> + 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_svm_dev *sdev = NULL;
>> struct intel_iommu *iommu = d;
>> struct intel_svm *svm = NULL;
>> int head, tail, handled = 0;
>> @@ -828,7 +883,6 @@ 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 vm_area_struct *vma;
>> struct page_req_dsc *req;
>> struct qi_desc resp;
>> @@ -864,6 +918,20 @@ 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 +942,17 @@ 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 +971,11 @@ 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. */
>> - rcu_read_unlock();
>> -
>> - if (WARN_ON(&sdev->list == &svm->devs))
>> - sdev = NULL;
>> -
>> +bad_req:
>> + WARN_ON(!sdev);
>> 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 +986,7 @@ 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 +1011,7 @@ 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
>
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