Re: [PATCH v10 03/12] iommu: Remove SVM_FLAG_SUPERVISOR_MODE support

[Yi Liu]

On 2022/7/5 13:07, Lu Baolu wrote:
> The current kernel DMA with PASID support is based on the SVA with a flag
> SVM_FLAG_SUPERVISOR_MODE. The IOMMU driver binds the kernel memory address
> space to a PASID of the device. The device driver programs the device with
> kernel virtual address (KVA) for DMA access. There have been security and
> functional issues with this approach:
>
> - The lack of IOTLB synchronization upon kernel page table updates.
>    (vmalloc, module/BPF loading, CONFIG_DEBUG_PAGEALLOC etc.)
> - Other than slight more protection, using kernel virtual address (KVA)
>    has little advantage over physical address. There are also no use
>    cases yet where DMA engines need kernel virtual addresses for in-kernel
>    DMA.
>
> This removes SVM_FLAG_SUPERVISOR_MODE support from the IOMMU interface.
> The device drivers are suggested to handle kernel DMA with PASID through
> the kernel DMA APIs.
>
> The drvdata parameter in iommu_sva_bind_device() and all callbacks is not
> needed anymore. Cleanup them as well.
>
> Link: https://lore.kernel.org/linux-iommu/20210511194726.GP1002214@xxxxxxxxxx/
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Tested-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> Tested-by: Tony Zhu <tony.zhu@xxxxxxxxx>
> ---
>   include/linux/intel-iommu.h                   |  3 +-
>   include/linux/intel-svm.h                     | 13 -----
>   include/linux/iommu.h                         |  8 +--
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  5 +-
>   drivers/dma/idxd/cdev.c                       |  3 +-
>   drivers/dma/idxd/init.c                       | 25 +-------
>   .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   |  3 +-
>   drivers/iommu/intel/svm.c                     | 57 +++++--------------
>   drivers/iommu/iommu.c                         |  5 +-
>   drivers/misc/uacce/uacce.c                    |  2 +-
>   10 files changed, 26 insertions(+), 98 deletions(-)
>
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index e065cbe3c857..31e3edc0fc7e 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -738,8 +738,7 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn);
>   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);
> -struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm,
> -				 void *drvdata);
> +struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm);
>   void intel_svm_unbind(struct iommu_sva *handle);
>   u32 intel_svm_get_pasid(struct iommu_sva *handle);
>   int intel_svm_page_response(struct device *dev, struct iommu_fault_event *evt,
> diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
> index 207ef06ba3e1..f9a0d44f6fdb 100644
> --- a/include/linux/intel-svm.h
> +++ b/include/linux/intel-svm.h
> @@ -13,17 +13,4 @@
>   #define PRQ_RING_MASK	((0x1000 << PRQ_ORDER) - 0x20)
>   #define PRQ_DEPTH	((0x1000 << PRQ_ORDER) >> 5)
>   
> -/*
> - * The SVM_FLAG_SUPERVISOR_MODE flag requests a PASID which can be used only
> - * for access to kernel addresses. No IOTLB flushes are automatically done
> - * for kernel mappings; it is valid only for access to the kernel's static
> - * 1:1 mapping of physical memory — not to vmalloc or even module mappings.
> - * A future API addition may permit the use of such ranges, by means of an
> - * explicit IOTLB flush call (akin to the DMA API's unmap method).
> - *
> - * It is unlikely that we will ever hook into flush_tlb_kernel_range() to
> - * do such IOTLB flushes automatically.
> - */
> -#define SVM_FLAG_SUPERVISOR_MODE	BIT(0)
> -
>   #endif /* __INTEL_SVM_H__ */
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 418a1914a041..f41eb2b3c7da 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -243,8 +243,7 @@ struct iommu_ops {
>   	int (*dev_enable_feat)(struct device *dev, enum iommu_dev_features f);
>   	int (*dev_disable_feat)(struct device *dev, enum iommu_dev_features f);
>   
> -	struct iommu_sva *(*sva_bind)(struct device *dev, struct mm_struct *mm,
> -				      void *drvdata);
> +	struct iommu_sva *(*sva_bind)(struct device *dev, struct mm_struct *mm);
>   	void (*sva_unbind)(struct iommu_sva *handle);
>   	u32 (*sva_get_pasid)(struct iommu_sva *handle);
>   
> @@ -669,8 +668,7 @@ int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
>   bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
>   
>   struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> -					struct mm_struct *mm,
> -					void *drvdata);
> +					struct mm_struct *mm);
>   void iommu_sva_unbind_device(struct iommu_sva *handle);
>   u32 iommu_sva_get_pasid(struct iommu_sva *handle);
>   
> @@ -1012,7 +1010,7 @@ iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
>   }
>   
>   static inline struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
>   {
>   	return NULL;
>   }
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index cd48590ada30..d2ba86470c42 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -754,8 +754,7 @@ bool arm_smmu_master_sva_enabled(struct arm_smmu_master *master);
>   int arm_smmu_master_enable_sva(struct arm_smmu_master *master);
>   int arm_smmu_master_disable_sva(struct arm_smmu_master *master);
>   bool arm_smmu_master_iopf_supported(struct arm_smmu_master *master);
> -struct iommu_sva *arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm,
> -				    void *drvdata);
> +struct iommu_sva *arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm);
>   void arm_smmu_sva_unbind(struct iommu_sva *handle);
>   u32 arm_smmu_sva_get_pasid(struct iommu_sva *handle);
>   void arm_smmu_sva_notifier_synchronize(void);
> @@ -791,7 +790,7 @@ static inline bool arm_smmu_master_iopf_supported(struct arm_smmu_master *master
>   }
>   
>   static inline struct iommu_sva *
> -arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
> +arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
>   {
>   	return ERR_PTR(-ENODEV);
>   }
> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
> index c2808fd081d6..66720001ba1c 100644
> --- a/drivers/dma/idxd/cdev.c
> +++ b/drivers/dma/idxd/cdev.c
> @@ -6,7 +6,6 @@
>   #include <linux/pci.h>
>   #include <linux/device.h>
>   #include <linux/sched/task.h>
> -#include <linux/intel-svm.h>
>   #include <linux/io-64-nonatomic-lo-hi.h>
>   #include <linux/cdev.h>
>   #include <linux/fs.h>
> @@ -100,7 +99,7 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
>   	filp->private_data = ctx;
>   
>   	if (device_user_pasid_enabled(idxd)) {
> -		sva = iommu_sva_bind_device(dev, current->mm, NULL);
> +		sva = iommu_sva_bind_device(dev, current->mm);
>   		if (IS_ERR(sva)) {
>   			rc = PTR_ERR(sva);
>   			dev_err(dev, "pasid allocation failed: %d\n", rc);
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 355fb3ef4cbf..00b437f4f573 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -14,7 +14,6 @@
>   #include <linux/io-64-nonatomic-lo-hi.h>
>   #include <linux/device.h>
>   #include <linux/idr.h>
> -#include <linux/intel-svm.h>
>   #include <linux/iommu.h>
>   #include <uapi/linux/idxd.h>
>   #include <linux/dmaengine.h>
> @@ -466,29 +465,7 @@ static struct idxd_device *idxd_alloc(struct pci_dev *pdev, struct idxd_driver_d
>   
>   static int idxd_enable_system_pasid(struct idxd_device *idxd)
>   {
> -	int flags;
> -	unsigned int pasid;
> -	struct iommu_sva *sva;
> -
> -	flags = SVM_FLAG_SUPERVISOR_MODE;
> -
> -	sva = iommu_sva_bind_device(&idxd->pdev->dev, NULL, &flags);
> -	if (IS_ERR(sva)) {
> -		dev_warn(&idxd->pdev->dev,
> -			 "iommu sva bind failed: %ld\n", PTR_ERR(sva));
> -		return PTR_ERR(sva);
> -	}
> -
> -	pasid = iommu_sva_get_pasid(sva);
> -	if (pasid == IOMMU_PASID_INVALID) {
> -		iommu_sva_unbind_device(sva);
> -		return -ENODEV;
> -	}
> -
> -	idxd->sva = sva;
> -	idxd->pasid = pasid;
> -	dev_dbg(&idxd->pdev->dev, "system pasid: %u\n", pasid);
> -	return 0;
> +	return -EOPNOTSUPP;

this makes it to be a always fail call. right? will it break any
existing idxd usage?

>   }
>   
>   static void idxd_disable_system_pasid(struct idxd_device *idxd)
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> index 1ef7bbb4acf3..f155d406c5d5 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> @@ -367,8 +367,7 @@ __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
>   	return ERR_PTR(ret);
>   }
>   
> -struct iommu_sva *
> -arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
> +struct iommu_sva *arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
>   {
>   	struct iommu_sva *handle;
>   	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index 7ee37d996e15..d04880a291c3 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -313,8 +313,7 @@ static int pasid_to_svm_sdev(struct device *dev, unsigned int pasid,
>   	return 0;
>   }
>   
> -static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm,
> -				 unsigned int flags)
> +static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm)
>   {
>   	ioasid_t max_pasid = dev_is_pci(dev) ?
>   			pci_max_pasids(to_pci_dev(dev)) : intel_pasid_max_id;
> @@ -324,8 +323,7 @@ static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm,
>   
>   static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,

would be great to see a cleanup to rename the svm terms in intel iommu
driver to be sva. :-)

>   					   struct device *dev,
> -					   struct mm_struct *mm,
> -					   unsigned int flags)
> +					   struct mm_struct *mm)
>   {
>   	struct device_domain_info *info = dev_iommu_priv_get(dev);
>   	unsigned long iflags, sflags;
> @@ -341,22 +339,18 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
>   
>   		svm->pasid = mm->pasid;
>   		svm->mm = mm;
> -		svm->flags = flags;
>   		INIT_LIST_HEAD_RCU(&svm->devs);
>   
> -		if (!(flags & SVM_FLAG_SUPERVISOR_MODE)) {
> -			svm->notifier.ops = &intel_mmuops;
> -			ret = mmu_notifier_register(&svm->notifier, mm);
> -			if (ret) {
> -				kfree(svm);
> -				return ERR_PTR(ret);
> -			}
> +		svm->notifier.ops = &intel_mmuops;
> +		ret = mmu_notifier_register(&svm->notifier, mm);
> +		if (ret) {
> +			kfree(svm);
> +			return ERR_PTR(ret);
>   		}
>   
>   		ret = pasid_private_add(svm->pasid, svm);
>   		if (ret) {
> -			if (svm->notifier.ops)
> -				mmu_notifier_unregister(&svm->notifier, mm);
> +			mmu_notifier_unregister(&svm->notifier, mm);
>   			kfree(svm);
>   			return ERR_PTR(ret);
>   		}
> @@ -391,9 +385,7 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
>   	}
>   
>   	/* Setup the pasid table: */
> -	sflags = (flags & SVM_FLAG_SUPERVISOR_MODE) ?
> -			PASID_FLAG_SUPERVISOR_MODE : 0;
> -	sflags |= cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
> +	sflags = cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
>   	spin_lock_irqsave(&iommu->lock, iflags);
>   	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm->pasid,
>   					    FLPT_DEFAULT_DID, sflags);
> @@ -410,8 +402,7 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
>   	kfree(sdev);
>   free_svm:
>   	if (list_empty(&svm->devs)) {
> -		if (svm->notifier.ops)
> -			mmu_notifier_unregister(&svm->notifier, mm);
> +		mmu_notifier_unregister(&svm->notifier, mm);
>   		pasid_private_remove(mm->pasid);
>   		kfree(svm);
>   	}
> @@ -767,7 +758,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>   			 * to unbind the mm while any page faults are outstanding.
>   			 */
>   			svm = pasid_private_find(req->pasid);
> -			if (IS_ERR_OR_NULL(svm) || (svm->flags & SVM_FLAG_SUPERVISOR_MODE))
> +			if (IS_ERR_OR_NULL(svm))
>   				goto bad_req;
>   		}
>   
> @@ -818,40 +809,20 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>   	return IRQ_RETVAL(handled);
>   }
>   
> -struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
> +struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm)
>   {
>   	struct intel_iommu *iommu = device_to_iommu(dev, NULL, NULL);
> -	unsigned int flags = 0;
>   	struct iommu_sva *sva;
>   	int ret;
>   
> -	if (drvdata)
> -		flags = *(unsigned int *)drvdata;
> -
> -	if (flags & SVM_FLAG_SUPERVISOR_MODE) {
> -		if (!ecap_srs(iommu->ecap)) {
> -			dev_err(dev, "%s: Supervisor PASID not supported\n",
> -				iommu->name);
> -			return ERR_PTR(-EOPNOTSUPP);
> -		}
> -
> -		if (mm) {
> -			dev_err(dev, "%s: Supervisor PASID with user provided mm\n",
> -				iommu->name);
> -			return ERR_PTR(-EINVAL);
> -		}
> -
> -		mm = &init_mm;
> -	}
> -
>   	mutex_lock(&pasid_mutex);
> -	ret = intel_svm_alloc_pasid(dev, mm, flags);
> +	ret = intel_svm_alloc_pasid(dev, mm);
>   	if (ret) {
>   		mutex_unlock(&pasid_mutex);
>   		return ERR_PTR(ret);
>   	}
>   
> -	sva = intel_svm_bind_mm(iommu, dev, mm, flags);
> +	sva = intel_svm_bind_mm(iommu, dev, mm);
>   	mutex_unlock(&pasid_mutex);
>   
>   	return sva;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 0cb0750f61e8..74a0a3ec0907 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2788,7 +2788,6 @@ EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
>    * iommu_sva_bind_device() - Bind a process address space to a device
>    * @dev: the device
>    * @mm: the mm to bind, caller must hold a reference to it
> - * @drvdata: opaque data pointer to pass to bind callback
>    *
>    * Create a bond between device and address space, allowing the device to access
>    * the mm using the returned PASID. If a bond already exists between @device and
> @@ -2801,7 +2800,7 @@ EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
>    * On error, returns an ERR_PTR value.
>    */
>   struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
>   {
>   	struct iommu_group *group;
>   	struct iommu_sva *handle = ERR_PTR(-EINVAL);
> @@ -2826,7 +2825,7 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
>   	if (iommu_group_device_count(group) != 1)
>   		goto out_unlock;
>   
> -	handle = ops->sva_bind(dev, mm, drvdata);
> +	handle = ops->sva_bind(dev, mm);
>   
>   out_unlock:
>   	mutex_unlock(&group->mutex);
> diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> index 281c54003edc..3238a867ea51 100644
> --- a/drivers/misc/uacce/uacce.c
> +++ b/drivers/misc/uacce/uacce.c
> @@ -99,7 +99,7 @@ static int uacce_bind_queue(struct uacce_device *uacce, struct uacce_queue *q)
>   	if (!(uacce->flags & UACCE_DEV_SVA))
>   		return 0;
>   
> -	handle = iommu_sva_bind_device(uacce->parent, current->mm, NULL);
> +	handle = iommu_sva_bind_device(uacce->parent, current->mm);
>   	if (IS_ERR(handle))
>   		return PTR_ERR(handle);
>   

--
Regards,
Yi Liu