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Date: Fri, 10 Jul 2020 16:17:30 +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 4/4] iommu/vt-d: Add page response ops support
Hi Kevin,
On 2020/7/10 13:49, Tian, Kevin wrote:
>> 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?
>
It's in local tree, not upstream yet.
Best regards,
baolu
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