Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1185896 > unrolled thread

Re: [PATCH v2 01/20] xen: Add Xen specific page definition

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v2 01/20] xen: Add Xen specific page definition Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-07-16 16:30 +0200
    Re: [PATCH v2 01/20] xen: Add Xen specific page definition Julien Grall <julien.grall@citrix.com> - 2015-07-16 17:00 +0200

#1185896 — Re: [PATCH v2 01/20] xen: Add Xen specific page definition

On Thu, 9 Jul 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 page_to_pfn to use new Xen page definition.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> ---
>     I'm wondering if we should drop page_to_pfn has the macro will likely
>     misuse when Linux is using 64KB page granularity.
> 
>     Changes in v2:
>         - Add XEN_PFN_UP
>         - Add a comment describing the behavior of page_to_pfn
> ---
>  include/xen/page.h | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/include/xen/page.h b/include/xen/page.h
> index c5ed20b..8ebd37b 100644
> --- a/include/xen/page.h
> +++ b/include/xen/page.h
> @@ -1,11 +1,30 @@
>  #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)
> +#define xen_pfn_to_page(pfn)	\

I think it would be clearer if you called the parameter "xen_pfn"
instead of "pfn".


> +	((pfn_to_page(((unsigned long)(pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT)))
> +#define xen_page_to_pfn(page)	\
> +	(((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT)


It would be nice to have a comment:

/* assume PAGE_SIZE is a multiple of XEN_PAGE_SIZE */


> +#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 MFN associated to the first 4KB of the page */
>  static inline unsigned long page_to_mfn(struct page *page)
>  {
> -	return pfn_to_mfn(page_to_pfn(page));
> +	return pfn_to_mfn(xen_page_to_pfn(page));
>  }
>  
>  struct xen_memory_region {


Aside from the two minor suggestions:

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1185933

Hi Stefano,

On 16/07/2015 16:19, Stefano Stabellini wrote:
>> diff --git a/include/xen/page.h b/include/xen/page.h
>> index c5ed20b..8ebd37b 100644
>> --- a/include/xen/page.h
>> +++ b/include/xen/page.h
>> @@ -1,11 +1,30 @@
>>   #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)
>> +#define xen_pfn_to_page(pfn)	\
>
> I think it would be clearer if you called the parameter "xen_pfn"
> instead of "pfn".

Good idea, I will do it in the next version.

>
>> +	((pfn_to_page(((unsigned long)(pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT)))
>> +#define xen_page_to_pfn(page)	\
>> +	(((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT)
>
>
> It would be nice to have a comment:
>
> /* assume PAGE_SIZE is a multiple of XEN_PAGE_SIZE */

Ok. FWIW, there is already a BUILD_BUG_ON the privcmd driver to check 
this assumption (see patch #19).

I could move the BUILD_BUG_ON in page.h. Maybe inside xen_page_to_pfn?

>
>
>> +#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 MFN associated to the first 4KB of the page */
>>   static inline unsigned long page_to_mfn(struct page *page)
>>   {
>> -	return pfn_to_mfn(page_to_pfn(page));
>> +	return pfn_to_mfn(xen_page_to_pfn(page));
>>   }
>>
>>   struct xen_memory_region {
>
>
> Aside from the two minor suggestions:
>
> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

Thank you,

-- 
Julien Grall
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web