linux-kernel - Re: [Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page

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Message-ID: <55B205FB.5080209@citrix.com>
Date:	Fri, 24 Jul 2015 10:31:39 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Julien Grall <julien.grall@...rix.com>,
	<xen-devel@...ts.xenproject.org>
CC:	<ian.campbell@...rix.com>, <stefano.stabellini@...citrix.com>,
	<linux-kernel@...r.kernel.org>,
	David Vrabel <david.vrabel@...rix.com>,
	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split
 a Linux page into Xen page

On 09/07/15 21:42, Julien Grall wrote:
> The Xen interface is always using 4KB page. This means that a Linux page
> may be split across multiple Xen page when the page granularity is not
> the same.
> 
> This helper will break down a Linux page into 4KB chunk and call the
> helper on each of them.
[...]
> --- a/include/xen/page.h
> +++ b/include/xen/page.h
> @@ -39,4 +39,24 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
>  
>  extern unsigned long xen_released_pages;
>  
> +typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data);
> +
> +/* Break down the page in 4KB granularity and call fn foreach xen pfn */
> +static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn,
> +				    void *data)

I think this should be outlined (unless you have measurements that
support making it inlined).

Also perhaps make it

int xen_for_each_gfn(struct page *page,
                     xen_gfn_fn_t fn, void *data);

or

int xen_for_each_gfn(struct page **page, unsigned int count,
                     xen_gfn_fn_t fn, void *data);

?

David

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