linux-kernel - Re: [PATCH v2 5/5] mm: ptep

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Date:   Thu, 18 May 2023 09:08:16 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Ryan Roberts <ryan.roberts@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        SeongJae Park <sj@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Uladzislau Rezki <urezki@...il.com>, Zi Yan <ziy@...dia.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        damon@...ts.linux.dev, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 5/5] mm: ptep_deref() conversion

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@...dia.com>

Jason