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Subject: Re: [PATCH V10 06/11] iommu/vt-d: Add bind guest PASID support
To:     Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        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>
Cc:     Yi Liu <yi.l.liu@intel.com>, "Tian, Kevin" <kevin.tian@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Yi L <yi.l.liu@linux.intel.com>
References: <1584746861-76386-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1584746861-76386-7-git-send-email-jacob.jun.pan@linux.intel.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <62d2c2a1-0594-c647-1f2c-4d74c7b84d9a@redhat.com>
Date:   Sun, 29 Mar 2020 15:40:22 +0200
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Hi,

On 3/21/20 12:27 AM, Jacob Pan wrote:
> 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;
> +	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.
nit : "nor do we use the guest PASID". Well the guest PASID FLAG is
checked below and if set, svm->gpasid is set ;-)
> +	 */
> +	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;
nit: This check also is done in intel_pasid_setup_nested with an extra
check:
+	switch (addr_width) {
+	case ADDR_WIDTH_5LEVEL:
+		if (cpu_feature_enabled(X86_FEATURE_LA57) &&
+			cap_5lp_support(iommu->cap)) {

> +	}
> +
> +	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");
> +			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.
> +			 */
> +			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.
> +		 */
> +		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);
> +		}
nit: the above 4 lines are duplicated 3 times. Might be worth a helper.
> +		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");
unlimited tracing upon userspace call? Don't know what is the best policy.
> +		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.
> +		 */
> +		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
> +	 */
> +	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);
> +		/*
> +		 * 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.
> +				 */
> +				ioasid_set_data(pasid, NULL);
> +				kfree(svm);
> +			}
> +		}
> +		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 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.
> +		     */
>  	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
>  
> 
Thanks

Eric