Re: [PATCH v2 5/5] mm: ptep_deref() conversion

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	SeongJae Park <sj@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Uladzislau Rezki <urezki@gmail.com>, Zi Yan <ziy@nvidia.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	damon@lists.linux.dev, kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v2 5/5] mm: ptep_deref() conversion
Date: Thu, 18 May 2023 09:08:16 -0300	[thread overview]
Message-ID: <ZGYVMMumjG1p84c8@ziepe.ca> (raw)
In-Reply-To: <20230518110727.2106156-6-ryan.roberts@arm.com>

On Thu, May 18, 2023 at 12:07:27PM +0100, Ryan Roberts wrote:

> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 3d4dd9420c30..5680542f744f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -514,6 +514,7 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
>  			    bool write_fault)
>  {
>  	pte_t *ptep;
> +	pte_t pte;
>  	spinlock_t *ptl;
>  	int ret;
>  
> @@ -536,10 +537,12 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
>  			return ret;
>  	}
>  
> -	if (write_fault && !pte_write(*ptep))
> +	pte = ptep_deref(ptep);
> +
> +	if (write_fault && !pte_write(pte))
>  		ret = -EFAULT;
>  	else
> -		*pfn = pte_pfn(*ptep);
> +		*pfn = pte_pfn(pte);
>  
>  	pte_unmap_unlock(ptep, ptl);
>  	return ret;

This hunk looks Ok

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason