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Date: Fri, 10 Jul 2020 02:24:28 +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 3/4] iommu/vt-d: Report page request faults for guest
SVA
> 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.
> +
> + 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
a strong preference, thus:
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> + 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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