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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@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Annie Li 2011-12-12 18:14:42 +08:00 committed by Konrad Rzeszutek Wilk
parent 9dbc71d53c
commit 6666754b11
2 changed files with 85 additions and 0 deletions
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72
drivers/xen/grant-table.c
View File

@ -120,6 +120,17 @@ struct gnttab_ops {
* by bit operations.
*/
int (*query_foreign_access)(grant_ref_t ref);
/*
* Grant a domain to access a range of bytes within the page referred by
* an available grant entry. Ref parameter is reference of a grant entry
* which will be sub-page accessed, domid is id of grantee domain, frame
* is frame address of subpage grant, flags is grant type and flag
* information, page_off is offset of the range of bytes, and length is
* length of bytes to be accessed.
*/
void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
unsigned long frame, int flags,
unsigned page_off, unsigned length);
};
static struct gnttab_ops *gnttab_interface;
@ -261,6 +272,66 @@ 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, rc;
ref = get_free_entries(1);
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;
}
return ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
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 +884,7 @@ 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)

13
include/xen/grant_table.h
View File

@ -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);