Re: [PATCH v12 4/8] iommu/vt-d: Add bind guest PASID support

Jacob Pan
2020-04-27T20:28:16Z

On Fri, 24 Apr 2020 10:47:45 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Wednesday, April 22, 2020 2:53 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.
>
> Above description is not accurate. Guest PASID table updates don't
> 'result in' PASID cache flush automatically. What about:
> --
> The guest needs to invalidate the PASID cache for any update to
> guest PASID table. Those invalidation requests are intercepted
> by the VMM and passed down to the host as binding guest PASID
> calls.
> --
It is good to add more details, thanks.

> >
> > 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.
> >
> > .-------------. .---------------------------.
> > | 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 | 204
> > ++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/intel-iommu.h | 8 +-
> > include/linux/intel-svm.h | 17 ++++
> > 4 files changed, 232 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c
> > b/drivers/iommu/intel-iommu.c index 9c01e391a931..8862d6b0ef21
> > 100644 --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -6179,6 +6179,10 @@ 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
> > };
> >
> > static void quirk_iommu_igfx(struct pci_dev *dev)
> > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> > index 2998418f0a38..69b2070b843d 100644
> > --- a/drivers/iommu/intel-svm.c
> > +++ b/drivers/iommu/intel-svm.c
> > @@ -226,6 +226,210 @@ static LIST_HEAD(global_svm_list);
> > list_for_each_entry((sdev), &(svm)->devs, list) \
> > if ((d) != (sdev)->dev) {} else
> >
> > +static inline void intel_svm_free_if_empty(struct intel_svm *svm,
> > u64 pasid) +{
> > + if (list_empty(&svm->devs)) {
> > + ioasid_set_data(pasid, NULL);
> > + kfree(svm);
> > + }
> > +}
>
> Do we really need a function form instead of putting the 4 lines
> directly after the 'out' label?
>
it is more readable and good for code sharing.

> > +
> > +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 *dmar_domain;
> > + struct intel_svm_dev *sdev;
> > + struct intel_svm *svm;
> > + int ret = 0;
> > +
> > + if (WARN_ON(!iommu) || !data)
> > + return -EINVAL;
>
> well, why not checking !dev together?
This is kernel API, unlike iommu and data caller fills in dev directly.

>
> > +
> > + 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;
> > + } else {
> > + return -ENOTSUPP;
> > + }
> > +
> > + /*
> > + * We only check host PASID range, we have no knowledge to
> > check
> > + * guest PASID range.
> > + */
> > + if (data->hpasid <= 0 || data->hpasid >= PASID_MAX)
> > + return -EINVAL;
> > +
> > + dmar_domain = to_dmar_domain(domain);
> > +
> > + 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.
> > + */
> > + if (WARN_ON(list_empty(&svm->devs))) {
> > + ret = -EINVAL;
> > + goto out;
> > + }
> > +
> > + for_each_svm_dev(sdev, 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;
>
> in last review Eric raised the open about what about binding the same
> PASID to the same pdev multiple times. We discussed that should be
> disallowed. Here can you check whether aux_domain is enabled on pdev
> to restrict multiple-binding only for sub-devices?
Why aux_domain is sufficient? A pdev could have aux_domain enabled but
still bind pdev many times more than its mdevs.

Either we allow multiple bind or not.

>
> > + }
> > + } 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. We can drop the
> > following line
> > + * once VFIO and IOASID set check is in place.
> > + */
>
> there is no check below this comment. Following lines are simply
> initializing the svm fields.
>
What it meant to say is that once IOASID set is checked in VFIO layer,
we can drop the assignment of svm->mm, IOMMU driver will not check.

You are right, this is just a place holder to help handle many moving
pieces.

> > + 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);
> > + mmput(svm->mm);
> > + }
> > + sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
> > + if (!sdev) {
> > + /*
> > + * If this is a new PASID that never bond to a
> > device, then
> > + * the device list must be empty which indicates
> > struct svm
> > + * was allocated in this function.
> > + */
> > + intel_svm_free_if_empty(svm, data->hpasid);
> > + 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_ratelimited(dev, "Failed to enable PASID
> > capability\n");
>
> print hpasid

OK, sounds good.
>
> > + kfree(sdev);
> > + intel_svm_free_if_empty(svm, data->hpasid);
> > + goto out;
> > + }
> > +
> > + /*
> > + * PASID table is per device for better security.
> > Therefore, for
> > + * each bind of a new device even with an existing PASID,
> > we need to
> > + * call the nested mode setup function here.
> > + */
> > + spin_lock(&iommu->lock);
> > + ret = intel_pasid_setup_nested(iommu,
> > + dev,
> > + (pgd_t *)data->gpgd,
> > + data->hpasid,
> > + &data->vtd,
> > + dmar_domain,
> > + data->addr_width);
> > + if (ret) {
> > + dev_err_ratelimited(dev, "Failed to set up PASID
> > %llu in nested mode, Err %d\n",
> > + data->hpasid, ret);
> > + /*
> > + * PASID entry should be in cleared state if
> > nested mode
> > + * set up failed. So we only need to clear IOASID
> > tracking
> > + * data such that free call will succeed.
> > + */
> > + kfree(sdev);
> > + intel_svm_free_if_empty(svm, data->hpasid);
> > + spin_unlock(&iommu->lock);
> > + goto out;
> > + }
> > + spin_unlock(&iommu->lock);
>
> spin_unlock can be moved before if(ret)?
Yes, good point. We can combine the unlock.

>
> > + 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_iommu *iommu = intel_svm_device_to_iommu(dev);
> > + struct intel_svm_dev *sdev;
> > + struct intel_svm *svm;
> > + int ret = -EINVAL;
> > +
> > + if (WARN_ON(!iommu))
> > + return -EINVAL;
> > +
> > + mutex_lock(&pasid_mutex);
> > + svm = ioasid_find(NULL, pasid, NULL);
> > + if (!svm) {
> > + ret = -EINVAL;
> > + goto out;
> > + }
> > +
> > + if (IS_ERR(svm)) {
> > + ret = PTR_ERR(svm);
> > + goto out;
> > + }
> > +
> > + for_each_svm_dev(sdev, svm, dev) {
> > + ret = 0;
> > + sdev->users--;
> > + if (!sdev->users) {
> > + list_del_rcu(&sdev->list);
> > + intel_pasid_tear_down_entry(iommu, dev,
> > svm-
> > >pasid);
> > + intel_flush_svm_range_dev(svm, sdev, 0,
> > -1, 0);
> > + /* 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)) {
> > + /*
> > + * We do not free the IOASID here
> > in that
> > + * IOMMU driver did not allocate
> > it.
> > + * Unlike native SVM, IOASID for
> > guest use was
> > + * allocated prior to the bind
> > call.
> > + * In any case, if the free call
> > comes before
> > + * the unbind, IOMMU driver will
> > get notified
> > + * and perform cleanup.
> > + */
> > + ioasid_set_data(pasid, NULL);
> > + kfree(svm);
> > + }
>
> is it safer moving above empty check outside of the loop?
why? could you explain.

Note that this is not a loop.

>
> > + }
> > + 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 6da03f627ba3..c8ce2336f8d8
> > 100644 --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -706,7 +706,9 @@ struct dmar_domain *find_domain(struct device
> > *dev);
> > extern void intel_svm_check(struct intel_iommu *iommu);
> > extern int intel_svm_enable_prq(struct intel_iommu *iommu);
> > extern int intel_svm_finish_prq(struct intel_iommu *iommu);
> > -
> > +int intel_svm_bind_gpasid(struct iommu_domain *domain, struct
> > device *dev,
> > + struct iommu_gpasid_bind_data *data);
> > +int intel_svm_unbind_gpasid(struct device *dev, int pasid);
> > struct svm_dev_ops;
> >
> > struct intel_svm_dev {
> > @@ -723,9 +725,13 @@ 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.
> > + */
>
> /* in case that guest PASID is different from host PASID */
OK, will do.

>
> > struct list_head devs;
> > struct list_head list;
> > };
> > diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
> > index d7c403d0dd27..c19690937540 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
>
> this statement is confusing. We still have mm_struct in the host side
> to claim the ownership of a PASID.
>
How about this:
/*
* The SVM_FLAG_GUEST_MODE flag is used when a PASID bind is for guest
* processes. Compared to the host bind, the primary differences are:
* 1. mm life cycle management
* 2. fault reporting
*/

> > + * cycle is managed by VMM and VFIO layer. For IOMMU driver, this
> > API
>
> why is a flag becoming an API?
>
will refer as flag.

> > 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.
>
> I feel such example doesn't belong here, which is purely userspace
> policy. Here just describe what the flag is for should be sufficient.
>
Will remove the example. How about this?

/*
* 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.
*/

> > + */
> > +#define SVM_FLAG_GUEST_PASID (1<<3)
> >
> > #ifdef CONFIG_INTEL_IOMMU_SVM
> >
> > --
> > 2.7.4
>
> Thanks
> Kevin
>

[Jacob Pan]