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Date:   Fri, 25 Oct 2019 10:33:37 -0700
From:   Jacob Pan <jacob.jun.pan@linux.intel.com>
To:     "Tian, Kevin" <kevin.tian@intel.com>
Cc:     "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        "David Woodhouse" <dwmw2@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Eric Auger <eric.auger@redhat.com>,
        jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH v7 09/11] iommu/vt-d: Add bind guest PASID support
Message-ID: <20191025103337.1e51c0c9@jacob-builder>
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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]