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

[Tian, Kevin]

> From: Jacob Pan [mailto:jacob.jun.pan@xxxxxxxxxxxxxxx]
> Sent: Saturday, October 26, 2019 1:34 AM
> 
> Hi Kevin,
> 
> 
> On Fri, 25 Oct 2019 07:19:26 +0000
> "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
> 
> > > From: Jacob Pan [mailto:jacob.jun.pan@xxxxxxxxxxxxxxx]
> > > 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@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
> > > ---
> > >  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

I should say pure "scalable mode" logic. Above callbacks are not
related to host SVM per se. They are serving gpasid requests from
guest side, thus part of generic scalable mode capability.

> 
> > >  };
> > >
> > >  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.

one process, and there might be multiple threads each corresponding
to a vCPU.

> 
> > > +		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]