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SubjectRe: [PATCH V10 06/11] iommu/vt-d: Add bind guest PASID support
On Sat, 28 Mar 2020 08:02:01 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Saturday, March 21, 2020 7:28 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.
> >
> > 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 | 224
> > ++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/intel-iommu.h | 8 +-
> > include/linux/intel-svm.h | 17 ++++
> > 4 files changed, 252 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c
> > b/drivers/iommu/intel-iommu.c index e599b2537b1c..b1477cd423dd
> > 100644 --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -6203,6 +6203,10 @@ 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 d7f2a5358900..47c0deb5ae56 100644
> > --- a/drivers/iommu/intel-svm.c
> > +++ b/drivers/iommu/intel-svm.c
> > @@ -226,6 +226,230 @@ static LIST_HEAD(global_svm_list);
> > list_for_each_entry((sdev), &(svm)->devs, list) \
> > if ((d) != (sdev)->dev) {} else
> >
> > +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;
>
> what about the full name e.g. dmar_domain? though a bit longer
> but clearer than ddomain.
>
Sure, I don't have preference.

> > + 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;
> > + } else {
> > + return -ENOTSUPP;
> > + }
> > +
> > + /*
> > + * 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);
> > +
> > + /* Sanity check paging mode support match between host and
> > guest */
> > + if (data->addr_width == ADDR_WIDTH_5LEVEL &&
> > + !cap_5lp_support(iommu->cap)) {
> > + pr_err("Cannot support 5 level paging requested by
> > guest!\n");
> > + return -EINVAL;
> > + }
>
> -ENOTSUPP?
I was thinking from this API p.o.v, the input is invalid. Since both
cap and addr_width are derived from input arguments.

>
> > +
> > + 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;
> > + }
> > +
> > + if (svm->mm == get_task_mm(current) &&
> > + data->hpasid == svm->pasid &&
> > + data->gpasid == svm->gpasid) {
> > + pr_warn("Cannot bind the same guest-host
> > PASID for the same process\n");
>
> Sorry I didn’t get the rationale here. Isn't this branch is for
> binding the same PASID to multiple devices? In that case definitely
> it is binding the same guest-host PASID for the same process.
> otherwise if hpasid is different then you'll hit a different
> intel_svm, while if gpasid is different how you can use one intel_svm
> to hold multiple gpasids?
>
> I feel the error condition should be the opposite. and suppose
> SVM_FLAG_ GUEST_PASID should be verified before checking gpasid.
>
You are right, actually we don't need the check here. The
scenario for multiple devices bind to the same PASID is checked in
for_each_svm_dev()
I will remove this code.

> > + mmput(svm->mm);
> > + ret = -EINVAL;
> > + goto out;
> > + }
> > + mmput(current->mm);
> > +
> > + 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.
>
> Does sub-device mean mdev? I didn't find such notation in current
> iommu directory.
>
yes it is intended for mdev.
> and to make it clearer, "In case of multiple mdevs of the same pdev
> assigned to the same guest process".
>
I am avoiding mdev on purpose since it is not a concept in iommu
driver. sub-device is more generic.

> > + */
> > + sdev->users++;
> > + goto out;
> > + }
> > + } 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.
> > + */
>
> Above message is unclear about what should be revisited. Does it
> describe the current implementation or the expected revision in the
> future?
>
What I meant was if VFIO can check PASID-mm ownership by itself, then
we don;t have to store svm->mm here. Will drop the line below.
I will add this comment to clarify.

> > + 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 (list_empty(&svm->devs)) {
> > + ioasid_set_data(data->hpasid, NULL);
> > + 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);
> > + /*
> > + * If this this 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.
> > + */
>
> the comment better move to the 1st occurrence when sdev allocation
> fails. or even better put it in out label...
>
Sounds good.

> > + if (list_empty(&svm->devs)) {
> > + ioasid_set_data(data->hpasid, NULL);
> > + kfree(svm);
> > + }
> > + 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
> > + */
> looks above just explains the internal detail of
> intel_pasid_setup_nested, which is not necessary to be here.
>
Right, will remove the comments.

> > + ret = intel_pasid_setup_nested(iommu,
> > + dev,
> > + (pgd_t *)data->gpgd,
> > + data->hpasid,
> > + &data->vtd,
> > + ddomain,
> > + data->addr_width);
>
> It's worthy of an explanation here that setup_nested is required for
> every device (even when they are sharing same intel_svm) because
> we allocate pasid table per device. Otherwise I made a mistake to
> think that only the 1st device bound to a new hpasid requires this
> step. 😊
>
Good suggestion, I will add the comments as:
/*
* 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.
*/
> > + if (ret) {
> > + dev_err(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);
> > + if (list_empty(&svm->devs)) {
> > + ioasid_set_data(data->hpasid, NULL);
> > + kfree(svm);
> > + }
> > + 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_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);
> > + /* 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 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.
>
> As commented in other patches, VFIO is only one example user of this
> API...
>
Right, how about this:
/*
* 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);
> > + }
> > + }
> > + break;
> > + }
>
> what about no dev match? an -EINVAL is also required then.
>
Yes, ret is initialized as -EINVAL

> > +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 eda1d6687144..85b05120940e
> > 100644 --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -681,7 +681,9 @@ 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);
> > -
> > +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 {
> > @@ -698,9 +700,13 @@ 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.
> > + */
>
> we don't need to highlight identity or non-identity thing, since
> either way shares the same infrastructure here and it is not the
> knowledge that the kernel driver should assume
>
Sorry, I don't get your point.

What I meant was that this field "gpasid" is only used for non-identity
case. For identity case, we don't have SVM_FLAG_GUEST_PASID.

> > 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
> > + * 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]

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