Re: [PATCH v7 09/11] iommu/vt-d: Add bind guest PASID support

Jacob Pan
2019-10-25T17:29:18Z

Hi Kevin,

On Fri, 25 Oct 2019 07:19:26 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Jacob Pan [mailto:jacob.jun.pan@linux.intel.com]
> > Sent: Friday, October 25, 2019 3:55 AM
> >
> > When supporting guest SVA with emulated IOMMU, the guest PASID
> > table is shadowed in VMM. Updates to guest vIOMMU PASID table
> > will result in PASID cache flush which will be passed down to
> > the host as bind guest PASID calls.
>
> will be translated into binding/unbinding guest PASID calls to update
> the host shadow PASID table.
>
yours is more precise, will replace.
> >
> > For the SL page tables, it will be harvested from device's
> > default domain (request w/o PASID), or aux domain in case of
> > mediated device.
>
> harvested -> copied or linked to?
Kind of the same, but I agree copied is more technical and precise
term. Will change.

> >
> > .-------------. .---------------------------.
> > | vIOMMU | | Guest process CR3, FL only|
> > | | '---------------------------'
> > .----------------/
> > | PASID Entry |--- PASID cache flush -
> > '-------------' |
> > | | V
> > | | CR3 in GPA
> > '-------------'
> > Guest
> > ------| Shadow |--------------------------|--------
> > v v v
> > Host
> > .-------------. .----------------------.
> > | pIOMMU | | Bind FL for GVA-GPA |
> > | | '----------------------'
> > .----------------/ |
> > | PASID Entry | V (Nested xlate)
> > '----------------\.------------------------------.
> > | | |SL for GPA-HPA, default domain|
> > | | '------------------------------'
> > '-------------'
> > Where:
> > - FL = First level/stage one page tables
> > - SL = Second level/stage two page tables
> >
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> > ---
> > drivers/iommu/intel-iommu.c | 4 +
> > drivers/iommu/intel-svm.c | 184
> > ++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/intel-iommu.h | 8 +-
> > include/linux/intel-svm.h | 17 ++++
> > 4 files changed, 212 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c
> > b/drivers/iommu/intel-iommu.c index acd1ac787d8b..5fab32fbc4b4
> > 100644 --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -6026,6 +6026,10 @@ const struct iommu_ops intel_iommu_ops = {
> > .dev_disable_feat = intel_iommu_dev_disable_feat,
> > .is_attach_deferred =
> > intel_iommu_is_attach_deferred, .pgsize_bitmap =
> > INTEL_IOMMU_PGSIZES, +#ifdef CONFIG_INTEL_IOMMU_SVM
> > + .sva_bind_gpasid = intel_svm_bind_gpasid,
> > + .sva_unbind_gpasid = intel_svm_unbind_gpasid,
> > +#endif
>
> again, pure PASID management logic should be separated from SVM.
>
I am not following, these two functions are SVM functionality, not
pure PASID management which is already separated in ioasid.c

> > };
> >
> > static void quirk_iommu_igfx(struct pci_dev *dev)
> > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> > index a18b02a9709d..ae13a310cf96 100644
> > --- a/drivers/iommu/intel-svm.c
> > +++ b/drivers/iommu/intel-svm.c
> > @@ -216,6 +216,190 @@ static LIST_HEAD(global_svm_list);
> > list_for_each_entry(sdev, &svm->devs, list) \
> > if (dev == sdev->dev) \
> >
> > +int intel_svm_bind_gpasid(struct iommu_domain *domain,
> > + struct device *dev,
> > + struct iommu_gpasid_bind_data *data)
> > +{
> > + struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> > + struct dmar_domain *ddomain;
> > + struct intel_svm_dev *sdev;
> > + struct intel_svm *svm;
> > + int ret = 0;
> > +
> > + if (WARN_ON(!iommu) || !data)
> > + return -EINVAL;
> > +
> > + if (data->version != IOMMU_GPASID_BIND_VERSION_1 ||
> > + data->format != IOMMU_PASID_FORMAT_INTEL_VTD)
> > + return -EINVAL;
> > +
> > + if (dev_is_pci(dev)) {
> > + /* VT-d supports devices with full 20 bit PASIDs
> > only */
> > + if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
> > + return -EINVAL;
> > + }
>
> what about non-pci devices? It just moves forward w/o any check here?
>
Good catch, we only support PCI-device on Intel. Even mdev has to pass
the pdev to bind. Will add the else case.

> > +
> > + /*
> > + * We only check host PASID range, we have no knowledge to
> > check
> > + * guest PASID range nor do we use the guest PASID.
> > + */
> > + if (data->hpasid <= 0 || data->hpasid >= PASID_MAX)
> > + return -EINVAL;
> > +
> > + ddomain = to_dmar_domain(domain);
> > + /* REVISIT:
> > + * Sanity check adddress width and paging mode support
> > + * width matching in two dimensions:
> > + * 1. paging mode CPU <= IOMMU
> > + * 2. address width Guest <= Host.
> > + */
>
> Is lacking of above logic harmful? If not, we should add
>
It is better to add the check now, not solely rely on QEMU.

> > + mutex_lock(&pasid_mutex);
> > + svm = ioasid_find(NULL, data->hpasid, NULL);
> > + if (IS_ERR(svm)) {
> > + ret = PTR_ERR(svm);
> > + goto out;
> > + }
> > + if (svm) {
> > + /*
> > + * If we found svm for the PASID, there must be at
> > + * least one device bond, otherwise svm should be
> > freed.
> > + */
> > + BUG_ON(list_empty(&svm->devs));
> > +
> > + for_each_svm_dev(svm, dev) {
> > + /* In case of multiple sub-devices of the
> > same pdev assigned, we should
> > + * allow multiple bind calls with the same
> > PASID and pdev.
> > + */
> > + sdev->users++;
> > + goto out;
>
> sorry if I overlooked, but I didn't see any check on the PASID
> actually belonging to this process. At least should check the
> match between svm->mm and get_task_mm? also check
> whether a previous binding between this hpasid and gpasid
> already exists.
>
We had some discussions on whom should be responsible for checking
ownership. I tend to think VFIO is right place but I guess we can also
double check here.
Good point, we should check the same H-G PASID bind already exists.
> > + }
> > + } else {
> > + /* We come here when PASID has never been bond to a
> > device. */
> > + svm = kzalloc(sizeof(*svm), GFP_KERNEL);
> > + if (!svm) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > + /* REVISIT: upper layer/VFIO can track host
> > process that bind the PASID.
> > + * ioasid_set = mm might be sufficient for vfio to
> > check pasid VMM
> > + * ownership.
> > + */
>
> Is it correct to leave the check to the caller?
>
Ditto, we will double check. But since this is related to the guest, I
feel iommu driver check mm might be too restrictive. I am not sure if
any VMM could have more than one process? One process does alloc, the
other does bind.

> > + svm->mm = get_task_mm(current);
> > + svm->pasid = data->hpasid;
> > + if (data->flags & IOMMU_SVA_GPASID_VAL) {
> > + svm->gpasid = data->gpasid;
> > + svm->flags |= SVM_FLAG_GUEST_PASID;
> > + }
> > + ioasid_set_data(data->hpasid, svm);
> > + INIT_LIST_HEAD_RCU(&svm->devs);
> > + INIT_LIST_HEAD(&svm->list);
> > +
> > + mmput(svm->mm);
> > + }
> > + sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
> > + if (!sdev) {
> > + if (list_empty(&svm->devs))
> > + kfree(svm);
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > + sdev->dev = dev;
> > + sdev->users = 1;
> > +
> > + /* Set up device context entry for PASID if not enabled
> > already */
> > + ret = intel_iommu_enable_pasid(iommu, sdev->dev);
> > + if (ret) {
> > + dev_err(dev, "Failed to enable PASID
> > capability\n");
> > + kfree(sdev);
> > + goto out;
> > + }
> > +
> > + /*
> > + * For guest bind, we need to set up PASID table entry as
> > follows:
> > + * - FLPM matches guest paging mode
> > + * - turn on nested mode
> > + * - SL guest address width matching
> > + */
> > + ret = intel_pasid_setup_nested(iommu,
> > + dev,
> > + (pgd_t *)data->gpgd,
> > + data->hpasid,
> > + &data->vtd,
> > + ddomain,
> > + data->addr_width);
> > + if (ret) {
> > + dev_err(dev, "Failed to set up PASID %llu in
> > nested mode, Err %d\n",
> > + data->hpasid, ret);
> > + kfree(sdev);
>
> disable pasid? revert ioasid_set_data?
>
Good catch, will do.
> > + goto out;
> > + }
> > + svm->flags |= SVM_FLAG_GUEST_MODE;
> > +
> > + init_rcu_head(&sdev->rcu);
> > + list_add_rcu(&sdev->list, &svm->devs);
> > + out:
> > + mutex_unlock(&pasid_mutex);
> > + return ret;
> > +}
> > +
> > +int intel_svm_unbind_gpasid(struct device *dev, int pasid)
> > +{
> > + struct intel_svm_dev *sdev;
> > + struct intel_iommu *iommu;
> > + struct intel_svm *svm;
> > + int ret = -EINVAL;
> > +
> > + mutex_lock(&pasid_mutex);
> > + iommu = intel_svm_device_to_iommu(dev);
> > + if (!iommu)
> > + goto out;
> > +
> > + svm = ioasid_find(NULL, pasid, NULL);
> > + if (IS_ERR_OR_NULL(svm)) {
> > + ret = PTR_ERR(svm);
> > + goto out;
> > + }
> > +
> > + for_each_svm_dev(svm, dev) {
> > + ret = 0;
> > + sdev->users--;
> > + if (!sdev->users) {
> > + list_del_rcu(&sdev->list);
> > + intel_pasid_tear_down_entry(iommu, dev,
> > svm-
> > >pasid);
> > + /* TODO: Drain in flight PRQ for the PASID
> > since it
> > + * may get reused soon, we don't want to
> > + * confuse with its previous life.
> > + * intel_svm_drain_prq(dev, pasid);
> > + */
> > + kfree_rcu(sdev, rcu);
> > +
> > + if (list_empty(&svm->devs)) {
> > + list_del(&svm->list);
> > + kfree(svm);
> > + /*
> > + * We do not free PASID here until
> > explicit call
> > + * from VFIO to free. The PASID
> > life cycle
> > + * management is largely tied to
> > VFIO management
> > + * of assigned device life cycles.
> > In case of
> > + * guest exit without a explicit
> > free PASID call,
> > + * the responsibility lies in VFIO
> > layer to free
> > + * the PASIDs allocated for the
> > guest.
> > + * For security reasons, VFIO has
> > to track the
> > + * PASID ownership per guest
> > anyway to ensure
> > + * that PASID allocated by one
> > guest cannot be
> > + * used by another.
> > + */
> > + ioasid_set_data(pasid, NULL);
> > + }
> > + }
> > + break;
> > + }
> > + out:
> > + mutex_unlock(&pasid_mutex);
> > +
> > + return ret;
> > +}
> > +
> > int intel_svm_bind_mm(struct device *dev, int *pasid, int flags,
> > struct svm_dev_ops *ops)
> > {
> > struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> > diff --git a/include/linux/intel-iommu.h
> > b/include/linux/intel-iommu.h index 3dba6ad3e9ad..6c74c71b1ebf
> > 100644 --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -673,7 +673,9 @@ int intel_iommu_enable_pasid(struct intel_iommu
> > *iommu, struct device *dev);
> > int intel_svm_init(struct intel_iommu *iommu);
> > extern int intel_svm_enable_prq(struct intel_iommu *iommu);
> > extern int intel_svm_finish_prq(struct intel_iommu *iommu);
> > -
> > +extern int intel_svm_bind_gpasid(struct iommu_domain *domain,
> > + struct device *dev, struct iommu_gpasid_bind_data
> > *data); +extern int intel_svm_unbind_gpasid(struct device *dev, int
> > pasid); struct svm_dev_ops;
> >
> > struct intel_svm_dev {
> > @@ -690,9 +692,13 @@ struct intel_svm_dev {
> > struct intel_svm {
> > struct mmu_notifier notifier;
> > struct mm_struct *mm;
> > +
> > struct intel_iommu *iommu;
> > int flags;
> > int pasid;
> > + int gpasid; /* Guest PASID in case of vSVA bind with
> > non-identity host
> > + * to guest PASID mapping.
> > + */
> > struct list_head devs;
> > struct list_head list;
> > };
> > diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
> > index 94f047a8a845..a2c189ad0b01 100644
> > --- a/include/linux/intel-svm.h
> > +++ b/include/linux/intel-svm.h
> > @@ -44,6 +44,23 @@ struct svm_dev_ops {
> > * do such IOTLB flushes automatically.
> > */
> > #define SVM_FLAG_SUPERVISOR_MODE (1<<1)
> > +/*
> > + * The SVM_FLAG_GUEST_MODE flag is used when a guest process bind
> > to a device.
> > + * In this case the mm_struct is in the guest kernel or userspace,
> > its life
> > + * cycle is managed by VMM and VFIO layer. For IOMMU driver, this
> > API provides
> > + * means to bind/unbind guest CR3 with PASIDs allocated for a
> > device.
> > + */
> > +#define SVM_FLAG_GUEST_MODE (1<<2)
> > +/*
> > + * The SVM_FLAG_GUEST_PASID flag is used when a guest has its own
> > PASID space,
> > + * which requires guest and host PASID translation at both
> > directions. We keep
> > + * track of guest PASID in order to provide lookup service to
> > device drivers.
> > + * One such example is a physical function (PF) driver that
> > supports mediated
> > + * device (mdev) assignment. Guest programming of mdev
> > configuration space can
> > + * only be done with guest PASID, therefore PF driver needs to
> > find the matching
> > + * host PASID to program the real hardware.
> > + */
> > +#define SVM_FLAG_GUEST_PASID (1<<3)
> >
> > #ifdef CONFIG_INTEL_IOMMU_SVM
> >
> > --
> > 2.7.4
>

[Jacob Pan]