linux-kernel - Re: [PATCH v2 1/5] mm: vmalloc must set pte via arch code

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Message-ID: <20230524184721.GO4967@kernel.org>
Date:   Wed, 24 May 2023 21:47:21 +0300
From:   Mike Rapoport <rppt@...nel.org>
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, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 1/5] mm: vmalloc must set pte via arch code

On Thu, May 18, 2023 at 12:07:23PM +0100, Ryan Roberts wrote:
> It is bad practice to directly set pte entries within a pte table.
> Instead all modifications must go through arch-provided helpers such as
> set_pte_at() to give the arch code visibility and allow it to check
> (and potentially modify) the operation.
> 
> Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Acked-by: Lorenzo Stoakes <lstoakes@...il.com>
> Reviewed-by: Christoph Hellwig <hch@....de>

Reviewed-by: Mike Rapoport (IBM) <rppt@...nel.org>

> ---
>  mm/vmalloc.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 9683573f1225..48202ec5f79a 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2899,10 +2899,16 @@ struct vmap_pfn_data {
>  static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
>  {
>  	struct vmap_pfn_data *data = private;
> +	unsigned long pfn = data->pfns[data->idx];
> +	pte_t ptent;
>  
> -	if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
> +	if (WARN_ON_ONCE(pfn_valid(pfn)))
>  		return -EINVAL;
> -	*pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
> +
> +	ptent = pte_mkspecial(pfn_pte(pfn, data->prot));
> +	set_pte_at(&init_mm, addr, pte, ptent);
> +
> +	data->idx++;
>  	return 0;
>  }
>  
> -- 
> 2.25.1
> 
> 

-- 
Sincerely yours,
Mike.