Re: [PATCH 4/4] iommu/vt-d: Calculate and set flags for handle_mm_fault

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

On 2/19/21 5:31 AM, Jacob Pan wrote:
> Page requests are originated from the user page fault. Therefore, we
> shall set FAULT_FLAG_USER.
> 
> FAULT_FLAG_REMOTE indicates that we are walking an mm which is not
> guaranteed to be the same as the current->mm and should not be subject
> to protection key enforcement. Therefore, we should set FAULT_FLAG_REMOTE
> to avoid faults when both SVM and PKEY are used.
> 
> References: commit 1b2ee1266ea6 ("mm/core: Do not enforce PKEY permissions on remote mm access")
> Reviewed-by: Raj Ashok <ashok.raj@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>

Acked-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

> ---
>   drivers/iommu/intel/svm.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index ff7ae7cc17d5..7bfd20a24a60 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -1086,6 +1086,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>   	struct intel_iommu *iommu = d;
>   	struct intel_svm *svm = NULL;
>   	int head, tail, handled = 0;
> +	unsigned int flags = 0;
>   
>   	/* Clear PPR bit before reading head/tail registers, to
>   	 * ensure that we get a new interrupt if needed. */
> @@ -1186,9 +1187,11 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>   		if (access_error(vma, req))
>   			goto invalid;
>   
> -		ret = handle_mm_fault(vma, address,
> -				      req->wr_req ? FAULT_FLAG_WRITE : 0,
> -				      NULL);
> +		flags = FAULT_FLAG_USER | FAULT_FLAG_REMOTE;
> +		if (req->wr_req)
> +			flags |= FAULT_FLAG_WRITE;
> +
> +		ret = handle_mm_fault(vma, address, flags, NULL);
>   		if (ret & VM_FAULT_ERROR)
>   			goto invalid;
>   
>