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Message-ID: <alpine.DEB.2.02.1508101143180.11337@kaball.uk.xensource.com>
Date: Mon, 10 Aug 2015 11:44:48 +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>,
Thomas Gleixner <tglx@...utronix.de>,
"Ingo Molnar" <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
<x86@...nel.org>
Subject: Re: [PATCH v3 04/20] xen/grant: Introduce helpers to split a page
into grant
On Fri, 7 Aug 2015, Julien Grall wrote:
> Currently, a grant is always based on the Xen page granularity (i.e
> 4KB). When Linux is using a different page granularity, a single page
> will be split between multiple grants.
>
> The new helpers will be in charge to split the Linux page into grants and
^ of splitting
> call a function given by the caller on each grant.
>
> Also provide an helper to count the number of grants within a given
> contiguous region.
>
> Note that the x86/include/asm/xen/page.h is now including
> xen/interface/grant_table.h rather than xen/grant_table.h. It's
> necessary because xen/grant_table.h depends on asm/xen/page.h and will
> break the compilation. Furthermore, only definition in
> interface/grant_table.h was required.
^ is
> 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>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
>
> Changes in v3:
> - Fix error reported by checkpatch.pl
> - Typoes
> - s/pfn/xen_pfn/ in gnttab_foreach_grant
> - Drop the possibility to use less data. The complexity is moved
> in netback which is the only user
> - Rename gnttab_foreach_grant into gnttab_foreach_grant_in_range
> - s/offset/start/ in gnttab_count_grant and update the
> description of the parameter
> - s/mfn/gfn base on the new terminologies
> - Add EXPORT_SYMBOL_GPL for gnttab_foreach_grant_in_range
> - Use xen_offset_in_page and XEN_PFN_DOWN whenever it's possible
> - Fix compilation on x86.
>
> Changes in v2:
> - Patch added
> ---
> arch/x86/include/asm/xen/page.h | 2 +-
> drivers/xen/grant-table.c | 26 +++++++++++++++++++++++++
> include/xen/grant_table.h | 42 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index 0b762f6..501479e 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -12,7 +12,7 @@
> #include <asm/pgtable.h>
>
> #include <xen/interface/xen.h>
> -#include <xen/grant_table.h>
> +#include <xen/interface/grant_table.h>
> #include <xen/features.h>
>
> /* Xen machine address */
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 62f591f..94ae0fd 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -776,6 +776,32 @@ void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
> }
> EXPORT_SYMBOL_GPL(gnttab_batch_copy);
>
> +void gnttab_foreach_grant_in_range(struct page *page,
> + unsigned int offset,
> + unsigned int len,
> + xen_grant_fn_t fn,
> + void *data)
> +{
> + unsigned int goffset;
> + unsigned int glen;
> + unsigned long xen_pfn;
> +
> + len = min_t(unsigned int, PAGE_SIZE - offset, len);
> + goffset = xen_offset_in_page(offset);
> +
> + xen_pfn = xen_page_to_pfn(page) + XEN_PFN_DOWN(offset);
> +
> + while (len) {
> + glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);
> + fn(pfn_to_gfn(xen_pfn), goffset, glen, data);
> +
> + goffset = 0;
> + xen_pfn++;
> + len -= glen;
> + }
> +}
> +EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);
> +
> int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> struct gnttab_map_grant_ref *kmap_ops,
> struct page **pages, unsigned int count)
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 4478f4b..2a8ebe8 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -45,8 +45,10 @@
> #include <asm/xen/hypervisor.h>
>
> #include <xen/features.h>
> +#include <xen/page.h>
> #include <linux/mm_types.h>
> #include <linux/page-flags.h>
> +#include <linux/kernel.h>
>
> #define GNTTAB_RESERVED_XENSTORE 1
>
> @@ -224,4 +226,44 @@ static inline struct xen_page_foreign *xen_page_foreign(struct page *page)
> #endif
> }
>
> +/* Split Linux page in chunk of the size of the grant and call fn
> + *
> + * Parameters of fn:
> + * gfn: guest frame number
> + * offset: offset in the grant
> + * len: length of the data in the grant.
> + * data: internal information
> + */
> +typedef void (*xen_grant_fn_t)(unsigned long gfn, unsigned int offset,
> + unsigned int len, void *data);
> +
> +void gnttab_foreach_grant_in_range(struct page *page,
> + unsigned int offset,
> + unsigned int len,
> + xen_grant_fn_t fn,
> + void *data);
> +
> +/* Helper to get to call fn only on the first "grant chunk" */
> +static inline void gnttab_one_grant(struct page *page, unsigned int offset,
> + unsigned len, xen_grant_fn_t fn,
> + void *data)
> +{
> + /* The first request is limited to the size of one grant */
> + len = min_t(unsigned int, XEN_PAGE_SIZE - (offset & ~XEN_PAGE_MASK),
> + len);
> +
> + gnttab_foreach_grant_in_range(page, offset, len, fn, data);
> +}
> +
> +/* Get the number of grant in a specified region
> + *
> + * start: Offset from the beginning of the first page
> + * len: total length of data (can cross multiple page)
> + */
> +static inline unsigned int gnttab_count_grant(unsigned int start,
> + unsigned int len)
> +{
> + return XEN_PFN_UP(xen_offset_in_page(start) + len);
> +}
> +
> #endif /* __ASM_GNTTAB_H__ */
> --
> 2.1.4
>
--
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