Re: [PATCH v5 11/12] iommu: Per-domain I/O page fault handling

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Mon, May 02, 2022 at 09:48:41AM +0800, Lu Baolu wrote:
> Tweak the I/O page fault handling framework to route the page faults to
> the domain and call the page fault handler retrieved from the domain.
> This makes the I/O page fault handling framework possible to serve more
> usage scenarios as long as they have an IOMMU domain and install a page
> fault handler in it. Some unused functions are also removed to avoid
> dead code.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
>  drivers/iommu/iommu-sva-lib.h |  1 -
>  drivers/iommu/io-pgfault.c    | 64 ++++-------------------------------
>  drivers/iommu/iommu-sva-lib.c | 20 -----------
>  3 files changed, 7 insertions(+), 78 deletions(-)
> 
> diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
> index 5776b4c80cc1..e7813c6706fb 100644
> --- a/drivers/iommu/iommu-sva-lib.h
> +++ b/drivers/iommu/iommu-sva-lib.h
> @@ -8,7 +8,6 @@
>  #include <linux/ioasid.h>
>  #include <linux/mm_types.h>
>  
> -struct mm_struct *iommu_sva_find(ioasid_t pasid);
>  struct mm_struct *iommu_sva_domain_mm(struct iommu_domain *domain);
>  
>  /* I/O Page fault */
> diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
> index 1df8c1dcae77..8a2bb56e1474 100644
> --- a/drivers/iommu/io-pgfault.c
> +++ b/drivers/iommu/io-pgfault.c
> @@ -69,69 +69,18 @@ static int iopf_complete_group(struct device *dev, struct iopf_fault *iopf,
>  	return iommu_page_response(dev, &resp);
>  }
>  
> -static enum iommu_page_response_code
> -iopf_handle_single(struct iopf_fault *iopf)
> -{
> -	vm_fault_t ret;
> -	struct mm_struct *mm;
> -	struct vm_area_struct *vma;
> -	unsigned int access_flags = 0;
> -	unsigned int fault_flags = FAULT_FLAG_REMOTE;
> -	struct iommu_fault_page_request *prm = &iopf->fault.prm;
> -	enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
> -
> -	if (!(prm->flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID))
> -		return status;
> -
> -	mm = iommu_sva_find(prm->pasid);
> -	if (IS_ERR_OR_NULL(mm))
> -		return status;
> -
> -	mmap_read_lock(mm);
> -
> -	vma = find_extend_vma(mm, prm->addr);
> -	if (!vma)
> -		/* Unmapped area */
> -		goto out_put_mm;
> -
> -	if (prm->perm & IOMMU_FAULT_PERM_READ)
> -		access_flags |= VM_READ;
> -
> -	if (prm->perm & IOMMU_FAULT_PERM_WRITE) {
> -		access_flags |= VM_WRITE;
> -		fault_flags |= FAULT_FLAG_WRITE;
> -	}
> -
> -	if (prm->perm & IOMMU_FAULT_PERM_EXEC) {
> -		access_flags |= VM_EXEC;
> -		fault_flags |= FAULT_FLAG_INSTRUCTION;
> -	}
> -
> -	if (!(prm->perm & IOMMU_FAULT_PERM_PRIV))
> -		fault_flags |= FAULT_FLAG_USER;
> -
> -	if (access_flags & ~vma->vm_flags)
> -		/* Access fault */
> -		goto out_put_mm;
> -
> -	ret = handle_mm_fault(vma, prm->addr, fault_flags, NULL);
> -	status = ret & VM_FAULT_ERROR ? IOMMU_PAGE_RESP_INVALID :
> -		IOMMU_PAGE_RESP_SUCCESS;
> -
> -out_put_mm:
> -	mmap_read_unlock(mm);
> -	mmput(mm);
> -
> -	return status;
> -}
> -
>  static void iopf_handle_group(struct work_struct *work)
>  {
>  	struct iopf_group *group;
> +	struct iommu_domain *domain;
>  	struct iopf_fault *iopf, *next;
>  	enum iommu_page_response_code status = IOMMU_PAGE_RESP_SUCCESS;
>  
>  	group = container_of(work, struct iopf_group, work);
> +	domain = iommu_get_domain_for_dev_pasid(group->dev,
> +			group->last_fault.fault.prm.pasid);
> +	if (!domain || !domain->iopf_handler)
> +		status = IOMMU_PAGE_RESP_INVALID;
>  
>  	list_for_each_entry_safe(iopf, next, &group->faults, list) {
>  		/*
> @@ -139,7 +88,8 @@ static void iopf_handle_group(struct work_struct *work)
>  		 * faults in the group if there is an error.
>  		 */
>  		if (status == IOMMU_PAGE_RESP_SUCCESS)
> -			status = iopf_handle_single(iopf);
> +			status = domain->iopf_handler(&iopf->fault,
> +						      domain->fault_data);
>  
>  		if (!(iopf->fault.prm.flags &
>  		      IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE))
> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> index 05a7d2f0e46f..ae3595d60f38 100644
> --- a/drivers/iommu/iommu-sva-lib.c
> +++ b/drivers/iommu/iommu-sva-lib.c
> @@ -69,26 +69,6 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm,
>  	return ret;
>  }
>  
> -/* ioasid_find getter() requires a void * argument */
> -static bool __mmget_not_zero(void *mm)
> -{
> -	return mmget_not_zero(mm);
> -}
> -
> -/**
> - * iommu_sva_find() - Find mm associated to the given PASID
> - * @pasid: Process Address Space ID assigned to the mm
> - *
> - * On success a reference to the mm is taken, and must be released with mmput().
> - *
> - * Returns the mm corresponding to this PASID, or an error if not found.
> - */
> -struct mm_struct *iommu_sva_find(ioasid_t pasid)
> -{
> -	return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_find);
> -
>  /*
>   * Get or put an ioas for a shared memory.
>   */
> -- 
> 2.25.1
>