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

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2022/7/31 20:01, Yi Liu wrote:
> 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@nvidia.com/
>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
>> Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
>> Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
>> Tested-by: Tony Zhu <tony.zhu@intel.com>
>> ---
>>   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?

The existing implemenation is problematic. The right solution should be
to attach the default domain to a pasid of a device and handle the
kernel DMA through the formal DMA kernel APIs.

Jacob has already posted his v2 in the mailing list.

> 
>>   }
>>   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. :-)

SVM is the term in Intel VT-d spec which existed before the term SVA.
It makes sense to make the naming consitent anyway. :-)

>>                          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);
> 

Best regards,
baolu