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Date: Wed, 1 Jul 2020 10:27:22 +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 3/4] iommu/vt-d: Report page request faults for guest SVA
Hi Kevin,
Thanks a lot for reviewing my patches.
On 6/30/20 2:01 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Sunday, June 28, 2020 8:34 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.
>>
>> 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 | 83
>> +++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 80 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
>> index c23167877b2b..4800bb6f8794 100644
>> --- a/drivers/iommu/intel/svm.c
>> +++ b/drivers/iommu/intel/svm.c
>> @@ -815,6 +815,69 @@ 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 intel_iommu *iommu, struct page_req_dsc
>> *desc)
>> +{
>> + struct iommu_fault_event event;
>> + struct pci_dev *pdev;
>> + u8 bus, devfn;
>> + int ret = 0;
>> +
>> + memset(&event, 0, sizeof(struct iommu_fault_event));
>> + bus = PCI_BUS_NUM(desc->rid);
>> + devfn = desc->rid & 0xff;
>> + pdev = pci_get_domain_bus_and_slot(iommu->segment, bus, devfn);
>
> Is this step necessary? dev can be passed in (based on sdev), and more
> importantly iommu_report_device_fault already handles the ref counting
> e.g. get_device(dev) when fault handler is valid...
Yes, agreed. I will pass device in instead.
>
>> +
>> + if (!pdev) {
>> + pr_err("No PCI device found for PRQ [%02x:%02x.%d]\n",
>> + bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>> + return -ENODEV;
>> + }
>> +
>> + /* 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.
>> + */
>> + 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;
>
> why setting lpig under this condition?
/*
* 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 feature beyond
* PCI ATS spec.
*/
>
>> + event.fault.prm.flags |=
>> IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA;
>> + memcpy(event.fault.prm.private_data, desc->priv_data,
>> + sizeof(desc->priv_data));
>> + }
>> +
>> + ret = iommu_report_device_fault(&pdev->dev, &event);
>> + pci_dev_put(pdev);
>> +
>> + return ret;
>> +}
>> +
>> static irqreturn_t prq_event_thread(int irq, void *d)
>> {
>> struct intel_iommu *iommu = d;
>> @@ -874,6 +937,19 @@ 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) {
>> + int res = intel_svm_prq_report(iommu, req);
>> +
>> + if (!res)
>> + goto prq_advance;
>> + else
>> + goto bad_req;
>> + }
>> +
>
> I noted in bad_req there is another reporting logic:
>
> 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);
> sdev->ops->fault_cb(sdev->dev, req->pasid, req->addr,
> req->priv_data, rwxp, result);
> }
>
> It was introduced in the 1st version of svm.c. It might be unrelated to
> this patch, but I wonder whether that one should be replaced with
> iommu_report_device_fault too?
This call back will be deprecated. The previous api in generic iommu has
been removed.
https://www.spinics.net/lists/iommu/msg43657.html
I will make it in a separated patch.
>
> Thanks
> Kevin
Best regards,
baolu
>
>> /* If the mm is already defunct, don't handle faults. */
>> if (!mmget_not_zero(svm->mm))
>> goto bad_req;
>> @@ -892,10 +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:
>> +bad_req:
>> /* Accounting for major/minor faults? */
>> rcu_read_lock();
>> list_for_each_entry_rcu(sdev, &svm->devs, list) {
>> @@ -920,7 +996,7 @@ 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 +1021,7 @@ 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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