linux-kernel - Re: [PATCH v3 03/20] xen: Add Xen specific page definition

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Message-ID: <alpine.DEB.2.02.1508101145380.11337@kaball.uk.xensource.com>
Date:	Mon, 10 Aug 2015 11:46:33 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Julien Grall <julien.grall@...rix.com>
CC:	<xen-devel@...ts.xenproject.org>,
	<linux-arm-kernel@...ts.infradead.org>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>, <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"David Vrabel" <david.vrabel@...rix.com>
Subject: Re: [PATCH v3 03/20] xen: Add Xen specific page definition

On Fri, 7 Aug 2015, Julien Grall wrote:
> The Xen hypercall interface is always using 4K page granularity on ARM
> and x86 architecture.
> 
> With the incoming support of 64K page granularity for ARM64 guest, it
> won't be possible to re-use the Linux page definition in Xen drivers.
> 
> Introduce Xen page definition helpers based on the Linux page
> definition. They have exactly the same name but prefixed with
> XEN_/xen_ prefix.
> 
> Also modify xen_page_to_gfn to use new Xen page definition.
> 
> Signed-off-by: Julien Grall <julien.grall@...rix.com>
> Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> 
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> 
>     Changes in v3:
>         - Fix errors reported by checkpatch.pl
>         - Rename pfn to xen_pfn in xen_pfn_to_page
>         - Add a comment that we assume PAGE_SIZE to be a multiple of
>         XEN_PAGE_SIZE
>         - s/MFN/GFN/ according to new naming
>         - Add Stefano's reviewed-by
> 
>     Changes in v2:
>         - Add XEN_PFN_UP
>         - Add a comment describing the behavior of page_to_pfn
> ---
>  include/xen/page.h | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/include/xen/page.h b/include/xen/page.h
> index f202992..dac1b26 100644
> --- a/include/xen/page.h
> +++ b/include/xen/page.h
> @@ -1,11 +1,36 @@
>  #ifndef _XEN_PAGE_H
>  #define _XEN_PAGE_H
>  
> +#include <asm/page.h>
> +
> +/* The hypercall interface supports only 4KB page */
> +#define XEN_PAGE_SHIFT	12
> +#define XEN_PAGE_SIZE	(_AC(1, UL) << XEN_PAGE_SHIFT)
> +#define XEN_PAGE_MASK	(~(XEN_PAGE_SIZE-1))
> +#define xen_offset_in_page(p)	((unsigned long)(p) & ~XEN_PAGE_MASK)
> +
> +/*
> + * We asume that PAGE_SIZE is a multiple of XEN_PAGE_SIZE
          ^ assume

> + * XXX: Add a BUILD_BUG_ON?
> + */
> +
> +#define xen_pfn_to_page(xen_pfn)	\
> +	((pfn_to_page(((unsigned long)(xen_pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT)))
> +#define xen_page_to_pfn(page)	\
> +	(((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT)
> +
> +#define XEN_PFN_PER_PAGE	(PAGE_SIZE / XEN_PAGE_SIZE)
> +
> +#define XEN_PFN_DOWN(x)	((x) >> XEN_PAGE_SHIFT)
> +#define XEN_PFN_UP(x)	(((x) + XEN_PAGE_SIZE-1) >> XEN_PAGE_SHIFT)
> +#define XEN_PFN_PHYS(x)	((phys_addr_t)(x) << XEN_PAGE_SHIFT)
> +
>  #include <asm/xen/page.h>
>  
> +/* Return the GFN associated to the first 4KB of the page */
>  static inline unsigned long xen_page_to_gfn(struct page *page)
>  {
> -	return pfn_to_gfn(page_to_pfn(page));
> +	return pfn_to_gfn(xen_page_to_pfn(page));
>  }
>  
>  struct xen_memory_region {
> -- 
> 2.1.4
> 
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