linux-kernel - Re: [PATCH v3 03/17] Xen: xlate: Use page_to_xen_pfn instead of page_to

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Date:	Mon, 25 Jan 2016 13:55:01 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Shannon Zhao <zhaoshenglong@...wei.com>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<ard.biesheuvel@...aro.org>, <mark.rutland@....com>,
	<stefano.stabellini@...rix.com>, <david.vrabel@...rix.com>,
	<catalin.marinas@....com>, <will.deacon@....com>,
	<julien.grall@...rix.com>, <xen-devel@...ts.xen.org>,
	<devicetree@...r.kernel.org>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <ian.campbell@...rix.com>,
	<shannon.zhao@...aro.org>, <peter.huangpeng@...wei.com>
Subject: Re: [PATCH v3 03/17] Xen: xlate: Use page_to_xen_pfn instead of
 page_to_pfn

On Sat, 23 Jan 2016, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@...aro.org>
> 
> Use page_to_xen_pfn in case of 64KB page.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@...aro.org>

Please update the commit message, something like:

"Make xen_xlate_map_ballooned_pages work with 64K pages. In that case
Kernel pages are 64K in size but Xen pages remain 4K in size. Xen pfns
refer to 4K pages."

Provided that you change the commit message:

Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


>  drivers/xen/xlate_mmu.c | 26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c
> index 9692656..28f728b 100644
> --- a/drivers/xen/xlate_mmu.c
> +++ b/drivers/xen/xlate_mmu.c
> @@ -207,9 +207,12 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
>  	void *vaddr;
>  	int rc;
>  	unsigned int i;
> +	unsigned long nr_pages;
> +	xen_pfn_t xen_pfn = 0;
>  
>  	BUG_ON(nr_grant_frames == 0);
> -	pages = kcalloc(nr_grant_frames, sizeof(pages[0]), GFP_KERNEL);
> +	nr_pages = DIV_ROUND_UP(nr_grant_frames, XEN_PFN_PER_PAGE);
> +	pages = kcalloc(nr_pages, sizeof(pages[0]), GFP_KERNEL);
>  	if (!pages)
>  		return -ENOMEM;
>  
> @@ -218,22 +221,25 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
>  		kfree(pages);
>  		return -ENOMEM;
>  	}
> -	rc = alloc_xenballooned_pages(nr_grant_frames, pages);
> +	rc = alloc_xenballooned_pages(nr_pages, pages);
>  	if (rc) {
> -		pr_warn("%s Couldn't balloon alloc %ld pfns rc:%d\n", __func__,
> -			nr_grant_frames, rc);
> +		pr_warn("%s Couldn't balloon alloc %ld pages rc:%d\n", __func__,
> +			nr_pages, rc);
>  		kfree(pages);
>  		kfree(pfns);
>  		return rc;
>  	}
> -	for (i = 0; i < nr_grant_frames; i++)
> -		pfns[i] = page_to_pfn(pages[i]);
> +	for (i = 0; i < nr_grant_frames; i++) {
> +		if ((i % XEN_PFN_PER_PAGE) == 0)
> +			xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
> +		pfns[i] = pfn_to_gfn(xen_pfn++);
> +	}
>  
> -	vaddr = vmap(pages, nr_grant_frames, 0, PAGE_KERNEL);
> +	vaddr = vmap(pages, nr_pages, 0, PAGE_KERNEL);
>  	if (!vaddr) {
> -		pr_warn("%s Couldn't map %ld pfns rc:%d\n", __func__,
> -			nr_grant_frames, rc);
> -		free_xenballooned_pages(nr_grant_frames, pages);
> +		pr_warn("%s Couldn't map %ld pages rc:%d\n", __func__,
> +			nr_pages, rc);
> +		free_xenballooned_pages(nr_pages, pages);
>  		kfree(pages);
>  		kfree(pfns);
>  		return -ENOMEM;
> -- 
> 2.0.4
> 
>