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Date: Thu, 8 Dec 2011 09:49:31 +0000
From: Paul Durrant <Paul.Durrant@...rix.com>
To: "annie.li@...cle.com" <annie.li@...cle.com>,
"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
"jeremy@...p.org" <jeremy@...p.org>,
Ian Campbell <Ian.Campbell@...rix.com>
CC: "kurt.hackel@...cle.com" <kurt.hackel@...cle.com>
Subject: RE: [PATCH V2 1/2] xen/granttable: Support sub-page grants
> -----Original Message-----
> From: annie.li@...cle.com [mailto:annie.li@...cle.com]
> Sent: 08 December 2011 09:37
> To: xen-devel@...ts.xensource.com; linux-kernel@...r.kernel.org;
> konrad.wilk@...cle.com; jeremy@...p.org; Paul Durrant; Ian Campbell
> Cc: kurt.hackel@...cle.com; annie.li@...cle.com
> Subject: [PATCH V2 1/2] xen/granttable: Support sub-page grants
>
> -- They can't be used to map the page (so can only be used in a
> GNTTABOP_copy
> hypercall).
> -- It's possible to grant access with a finer granularity than
> whole pages.
> -- Xen guarantees that they can be revoked quickly (a normal map
> grant can
> only be revoked with the cooperation of the domain which has
> been granted
> access).
>
> Signed-off-by: Annie Li <annie.li@...cle.com>
> ---
> drivers/xen/grant-table.c | 74
> +++++++++++++++++++++++++++++++++++++++++++++
> include/xen/grant_table.h | 13 ++++++++
> 2 files changed, 87 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index bd325fd..4a10e3f 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -120,6 +120,16 @@ struct gnttab_ops {
> * by bit operations.
> */
> int (*query_foreign_access)(grant_ref_t);
> + /*
> + * Grant a domain to access a range of bytes within the page
> referred by
> + * an available grant entry. First parameter is grant entry
> reference
> + * number, second one is id of grantee domain, third one is
> frame
> + * address of subpage grant, forth one is grant type and flag
> + * information, fifth one is offset of the range of bytes,
> and last one
> + * is length of bytes to be accessed.
> + */
> + void (*update_subpage_entry)(grant_ref_t, domid_t, unsigned
> long, int,
> + unsigned, unsigned);
> };
>
> static struct gnttab_ops *gnttab_interface; @@ -261,6 +271,69 @@
> int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
> } EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
>
> +void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
> + unsigned long frame, int flags,
> + unsigned page_off,
> + unsigned length)
> +{
> + gnttab_shared.v2[ref].sub_page.frame = frame;
> + gnttab_shared.v2[ref].sub_page.page_off = page_off;
> + gnttab_shared.v2[ref].sub_page.length = length;
> + gnttab_shared.v2[ref].hdr.domid = domid;
> + wmb();
> + gnttab_shared.v2[ref].hdr.flags =
> + GTF_permit_access | GTF_sub_page |
> flags; }
> +
> +int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref,
> domid_t domid,
> + unsigned long frame, int
> flags,
> + unsigned page_off,
> + unsigned length)
> +{
> + if (flags & (GTF_accept_transfer | GTF_reading |
> + GTF_writing | GTF_transitive))
> + return -EPERM;
> +
> + if (gnttab_interface->update_subpage_entry == NULL)
> + return -ENOSYS;
> +
> + gnttab_interface->update_subpage_entry(ref, domid, frame,
> flags,
> + page_off, length);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);
> +
> +int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned
> long frame,
> + int flags, unsigned page_off,
> + unsigned length)
> +{
> + int ref;
> +
> + if (flags & (GTF_accept_transfer | GTF_reading |
> + GTF_writing | GTF_transitive))
> + return -EPERM;
> +
> + if (gnttab_interface->update_subpage_entry == NULL)
> + return -ENOSYS;
> +
> + ref = get_free_entries(1);
> + if (unlikely(ref < 0))
> + return -ENOSPC;
> +
> + gnttab_interface->update_subpage_entry(ref, domid, frame,
> flags,
> + page_off, length);
> +
> + return ref;
> +}
> +EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
There's quite a lot of duplicated code here. What about something along the lines of:
#define get_free_entry() get_free_entries(1)
int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
int flags, unsigned page_off,
unsigned length)
{
int ref;
ref = get_free_entry();
if (unlikely(ref < 0))
return -ENOSPC;
rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags, page_off, length);
if (rc < 0)
put_free_entry(ref);
return (rc < 0) rc : ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
I think this is more akin to the format for existing non-ref variants.
> +
> +bool gnttab_subpage_grants_available(void)
> +{
> + return gnttab_interface->update_subpage_entry != NULL; }
> +EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);
> +
> static int gnttab_query_foreign_access_v1(grant_ref_t ref) {
> return gnttab_shared.v1[ref].flags &
> (GTF_reading|GTF_writing); @@ -813,6 +886,7 @@ static struct
> gnttab_ops gnttab_v2_ops = {
> .end_foreign_access_ref =
> gnttab_end_foreign_access_ref_v2,
> .end_foreign_transfer_ref =
> gnttab_end_foreign_transfer_ref_v2,
> .query_foreign_access =
> gnttab_query_foreign_access_v2,
> + .update_subpage_entry =
> gnttab_update_subpage_entry_v2,
> };
>
> static void gnttab_request_version(void) diff --git
> a/include/xen/grant_table.h b/include/xen/grant_table.h index
> fea4954..2b492b9 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -62,6 +62,15 @@ int gnttab_resume(void);
>
> int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
> int readonly);
> +int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned
> long frame,
> + int flags, unsigned page_off,
> + unsigned length);
> +
> +/*
> + * Are sub-page grants available on this version of Xen? Returns
> true
> +if they
> + * are, and false if they're not.
> + */
> +bool gnttab_subpage_grants_available(void);
>
> /*
> * End access through the given grant reference, iff the grant
> entry is no @@ -108,6 +117,10 @@ void
> gnttab_cancel_free_callback(struct gnttab_free_callback *callback);
>
> void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t
> domid,
> unsigned long frame, int readonly);
> +int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref,
> domid_t domid,
> + unsigned long frame, int
> flags,
> + unsigned page_off,
> + unsigned length);
>
> void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid,
> unsigned long pfn);
> --
> 1.7.6.4
--
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