Re: [PATCH 1/2] iommu/sva: Tighten SVA bind API with explicit flags

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

Hi Jean-Philippe,

On Fri, 9 Apr 2021 12:22:21 +0200, Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:

> On Thu, Apr 08, 2021 at 10:08:55AM -0700, Jacob Pan wrote:
> > The void* drvdata parameter isn't really used in iommu_sva_bind_device()
> > API,  
> 
> Right, it used to be a cookie passed to the device driver in the exit_mm()
> callback, but that went away with edcc40d2ab5f ("iommu: Remove
> iommu_sva_ops::mm_exit()")
> 
> > the current IDXD code "borrows" the drvdata for a VT-d private flag
> > for supervisor SVA usage.
> > 
> > Supervisor/Privileged mode request is a generic feature. It should be
> > promoted from the VT-d vendor driver to the generic code.
> > 
> > This patch replaces void* drvdata with a unsigned int flags parameter
> > and adjusts callers accordingly.  
> 
> Thanks for cleaning this up. Making flags unsigned long seems more common
> (I suggested int without thinking). But it doesn't matter much, we won't
> get to 32 flags.
> 
I was just thinking unsigned int is 32 bit for both 32 and 64 bit machine.

> > 
> > Link: https://lore.kernel.org/linux-iommu/YFhiMLR35WWMW%2FHu@myrica/
> > Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >  drivers/dma/idxd/cdev.c                         |  2 +-
> >  drivers/dma/idxd/init.c                         |  6 +++---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c |  2 +-
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h     |  4 ++--
> >  drivers/iommu/intel/Kconfig                     |  1 +
> >  drivers/iommu/intel/svm.c                       | 18 ++++++------------
> >  drivers/iommu/iommu.c                           |  9 ++++++---
> >  drivers/misc/uacce/uacce.c                      |  2 +-
> >  include/linux/intel-iommu.h                     |  2 +-
> >  include/linux/intel-svm.h                       | 17 ++---------------
> >  include/linux/iommu.h                           | 19
> > ++++++++++++++++--- 11 files changed, 40 insertions(+), 42 deletions(-)
> > 
> > diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
> > index 0db9b82..21ec82b 100644
> > --- a/drivers/dma/idxd/cdev.c
> > +++ b/drivers/dma/idxd/cdev.c
> > @@ -103,7 +103,7 @@ static int idxd_cdev_open(struct inode *inode,
> > struct file *filp) filp->private_data = ctx;
> >  
> >  	if (device_pasid_enabled(idxd)) {
> > -		sva = iommu_sva_bind_device(dev, current->mm, NULL);
> > +		sva = iommu_sva_bind_device(dev, current->mm, 0);
> >  		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 085a0c3..cdc85f1 100644
> > --- a/drivers/dma/idxd/init.c
> > +++ b/drivers/dma/idxd/init.c
> > @@ -300,13 +300,13 @@ static struct idxd_device *idxd_alloc(struct
> > pci_dev *pdev) 
> >  static int idxd_enable_system_pasid(struct idxd_device *idxd)
> >  {
> > -	int flags;
> > +	unsigned int flags;
> >  	unsigned int pasid;
> >  	struct iommu_sva *sva;
> >  
> > -	flags = SVM_FLAG_SUPERVISOR_MODE;
> > +	flags = IOMMU_SVA_BIND_SUPERVISOR;
> >  
> > -	sva = iommu_sva_bind_device(&idxd->pdev->dev, NULL, &flags);
> > +	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));
> > 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
> > bb251ca..23e287e 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 @@ -354,7 +354,7 @@
> > __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm) }
> >  
> >  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,
> > unsigned int flags)  
> 
> Could you add a check on flags:
> 
> 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
> bb251cab61f3..145ceb2fc5da 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 @@ -354,12 +354,15 @@
> __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm) }
> 
>  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,
> unsigned int flags) {
>  	struct iommu_sva *handle;
>  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>  	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> 
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
yes, will do.

>  	if (smmu_domain->stage != ARM_SMMU_DOMAIN_S1)
>  		return ERR_PTR(-EINVAL);
> 
> 
> 
> >  {
> >  	struct iommu_sva *handle;
> >  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> > 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 f985817..b971d4d
> > 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > @@ -711,7 +711,7 @@ 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); struct iommu_sva *arm_smmu_sva_bind(struct
> > device *dev, struct mm_struct *mm,
> > -				    void *drvdata);
> > +				    unsigned int flags);
> >  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);
> > @@ -742,7 +742,7 @@ static inline int
> > arm_smmu_master_disable_sva(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,
> > unsigned int flags) {
> >  	return ERR_PTR(-ENODEV);
> >  }
> > diff --git a/drivers/iommu/intel/Kconfig b/drivers/iommu/intel/Kconfig
> > index 28a3d15..5415052 100644
> > --- a/drivers/iommu/intel/Kconfig
> > +++ b/drivers/iommu/intel/Kconfig
> > @@ -41,6 +41,7 @@ config INTEL_IOMMU_SVM
> >  	select PCI_PRI
> >  	select MMU_NOTIFIER
> >  	select IOASID
> > +	select IOMMU_SVA_LIB  
> 
> Not needed here?
intel/svm.c is registered to sva-lib and use the IOMMU_SVA_BIND_SUPERVISOR
flag.

> 
> >  	help
> >  	  Shared Virtual Memory (SVM) provides a facility for devices
> >  	  to access DMA resources through process address space by
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index 574a7e6..4b5f8b0 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -486,12 +486,9 @@ intel_svm_bind_mm(struct device *dev, unsigned int
> > flags, } else
> >  		pasid_max = 1 << 20;
> >  
> > -	/* Bind supervisor PASID shuld have mm = NULL */
> > -	if (flags & SVM_FLAG_SUPERVISOR_MODE) {
> > -		if (!ecap_srs(iommu->ecap) || mm) {
> > -			pr_err("Supervisor PASID with user provided
> > mm.\n");
> > -			return -EINVAL;
> > -		}
> > +	if ((flags & IOMMU_SVA_BIND_SUPERVISOR) &&
> > !ecap_srs(iommu->ecap)) {
> > +		pr_err("Supervisor PASID not supported.\n");
> > +		return -EINVAL;
> >  	}
> >  
> >  	if (!(flags & SVM_FLAG_PRIVATE_PASID)) {
> > @@ -593,7 +590,7 @@ intel_svm_bind_mm(struct device *dev, unsigned int
> > flags, ret = intel_pasid_setup_first_level(iommu, dev,
> >  				mm ? mm->pgd : init_mm.pgd,
> >  				svm->pasid, FLPT_DEFAULT_DID,
> > -				(mm ? 0 : PASID_FLAG_SUPERVISOR_MODE) |
> > +				(mm ? 0 : IOMMU_SVA_BIND_SUPERVISOR) |
> >  				(cpu_feature_enabled(X86_FEATURE_LA57)
> > ? PASID_FLAG_FL5LP : 0));
> >  		spin_unlock_irqrestore(&iommu->lock, iflags);
> > @@ -620,7 +617,7 @@ intel_svm_bind_mm(struct device *dev, unsigned int
> > flags, ret = intel_pasid_setup_first_level(iommu, dev,
> >  						mm ? mm->pgd :
> > init_mm.pgd, svm->pasid, FLPT_DEFAULT_DID,
> > -						(mm ? 0 :
> > PASID_FLAG_SUPERVISOR_MODE) |
> > +						(mm ? 0 :
> > IOMMU_SVA_BIND_SUPERVISOR) | (cpu_feature_enabled(X86_FEATURE_LA57) ?
> >  						PASID_FLAG_FL5LP : 0));
> >  		spin_unlock_irqrestore(&iommu->lock, iflags);
> > @@ -1059,11 +1056,10 @@ static irqreturn_t prq_event_thread(int irq,
> > void *d) 
> >  #define to_intel_svm_dev(handle) container_of(handle, struct
> > intel_svm_dev, sva) struct iommu_sva *
> > -intel_svm_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
> > +intel_svm_bind(struct device *dev, struct mm_struct *mm, unsigned int
> > flags) {
> >  	struct iommu_sva *sva = ERR_PTR(-EINVAL);
> >  	struct intel_svm_dev *sdev = NULL;
> > -	unsigned int flags = 0;
> >  	int ret;
> >  
> >  	/*
> > @@ -1071,8 +1067,6 @@ intel_svm_bind(struct device *dev, struct
> > mm_struct *mm, void *drvdata)
> >  	 * It will require shared SVM data structures, i.e. combine
> > io_mm
> >  	 * and intel_svm etc.
> >  	 */
> > -	if (drvdata)
> > -		flags = *(unsigned int *)drvdata;
> >  	mutex_lock(&pasid_mutex);
> >  	ret = intel_svm_bind_mm(dev, flags, NULL, mm, &sdev);
> >  	if (ret)
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index d0b0a15..bf0a20f 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -2962,6 +2962,7 @@ EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
> >   * 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
> > + * @flags: options for the bind operation  
> 
> Could also specify valid flags "IOMMU_SVA_BIND_*"
> 
Good point! will do.

> >   *
> >   * 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 @@ -2974,7 +2975,7 @@
> > EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
> >   * 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, unsigned int flags) {
> >  	struct iommu_group *group;
> >  	struct iommu_sva *handle = ERR_PTR(-EINVAL);
> > @@ -2987,6 +2988,9 @@ iommu_sva_bind_device(struct device *dev, struct
> > mm_struct *mm, void *drvdata) if (!group)
> >  		return ERR_PTR(-ENODEV);
> >  
> > +	/* Supervisor SVA does not need the current mm */
> > +	if ((flags & IOMMU_SVA_BIND_SUPERVISOR) && mm)
> > +		return ERR_PTR(-EINVAL);
> >  	/* Ensure device count and domain don't change while we're
> > binding */ mutex_lock(&group->mutex);
> >  
> > @@ -2999,8 +3003,7 @@ 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, flags);
> >  out_unlock:
> >  	mutex_unlock(&group->mutex);
> >  	iommu_group_put(group);
> > diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> > index d07af4e..27e0e04 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, 0);
> >  	if (IS_ERR(handle))
> >  		return PTR_ERR(handle);
> >  
> > diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> > index 1bc46b8..cdff752 100644
> > --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -757,7 +757,7 @@ int intel_svm_bind_gpasid(struct iommu_domain
> > *domain, struct device *dev, struct iommu_gpasid_bind_data *data);
> >  int intel_svm_unbind_gpasid(struct device *dev, u32 pasid);
> >  struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct
> > *mm,
> > -				 void *drvdata);
> > +				 unsigned int flags);
> >  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 39d368a..ef6b753 100644
> > --- a/include/linux/intel-svm.h
> > +++ b/include/linux/intel-svm.h
> > @@ -30,30 +30,17 @@ struct svm_dev_ops {
> >   * if there is no other way to do so. It should be used sparingly, if
> > at all. */
> >  #define SVM_FLAG_PRIVATE_PASID		(1<<0)
> > -
> > -/*
> > - * 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	(1<<1)
> >  /*
> >   * The SVM_FLAG_GUEST_MODE flag is used when a PASID bind is for guest
> >   * processes. Compared to the host bind, the primary differences are:
> >   * 1. mm life cycle management
> >   * 2. fault reporting
> >   */
> > -#define SVM_FLAG_GUEST_MODE		(1<<2)
> > +#define SVM_FLAG_GUEST_MODE		(1<<1)
> >  /*
> >   * 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.
> >   */
> > -#define SVM_FLAG_GUEST_PASID		(1<<3)
> > +#define SVM_FLAG_GUEST_PASID		(1<<2)
> >  
> >  #endif /* __INTEL_SVM_H__ */
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 5e7fe51..a3fbaa2 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -166,6 +166,19 @@ enum iommu_dev_features {
> >  
> >  #ifdef CONFIG_IOMMU_API
> >  
> > +/*
> > + * The IOMMU_SVA_BIND_SUPERVISOR 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 IOMMU_SVA_BIND_SUPERVISOR       BIT(0)
> > +  
> 
> It needs to be defined before the #ifdef CONFIG_IOMMU_API, otherwise
> drivers using it won't build with !CONFIG_IOMMU_API
> 
Good point, I was counting on driver that uses SVA must depend on
CONFIG_IOMMU_API. But SVA could be an option of the driver itself.

> Thanks,
> Jean
> 
> >  /**
> >   * struct iommu_iotlb_gather - Range information for a pending IOTLB
> > flush *
> > @@ -287,7 +300,7 @@ struct iommu_ops {
> >  	int (*aux_get_pasid)(struct iommu_domain *domain, struct
> > device *dev); 
> >  	struct iommu_sva *(*sva_bind)(struct device *dev, struct
> > mm_struct *mm,
> > -				      void *drvdata);
> > +				      unsigned int flags);
> >  	void (*sva_unbind)(struct iommu_sva *handle);
> >  	u32 (*sva_get_pasid)(struct iommu_sva *handle);
> >  
> > @@ -640,7 +653,7 @@ int iommu_aux_get_pasid(struct iommu_domain
> > *domain, struct device *dev); 
> >  struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> >  					struct mm_struct *mm,
> > -					void *drvdata);
> > +					unsigned int flags);
> >  void iommu_sva_unbind_device(struct iommu_sva *handle);
> >  u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> >  
> > @@ -1015,7 +1028,7 @@ iommu_aux_get_pasid(struct iommu_domain *domain,
> > struct device *dev) }
> >  
> >  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, unsigned int flags) {
> >  	return NULL;
> >  }
> > -- 
> > 2.7.4
> >   


Thanks,

Jacob
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