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/*
****************************************************************************
* (C) 2006 - Cambridge University
****************************************************************************
*
* File: gnttab.c
* Author: Steven Smith (sos22@cam.ac.uk)
* Changes: Grzegorz Milos (gm281@cam.ac.uk)
*
* Date: July 2006
*
* Environment: Xen Minimal OS
* Description: Simple grant tables implementation. About as stupid as it's
* possible to be and still work.
*
****************************************************************************
*/
#include <mini-os/os.h>
#include <mini-os/mm.h>
#include <mini-os/gnttab.h>
#include <mini-os/semaphore.h>
#define NR_RESERVED_ENTRIES 8
/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
#define NR_GRANT_FRAMES 4
#define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * PAGE_SIZE / sizeof(grant_entry_t))
static grant_entry_t *gnttab_table;
static grant_ref_t gnttab_list[NR_GRANT_ENTRIES];
#ifdef GNT_DEBUG
static char inuse[NR_GRANT_ENTRIES];
#endif
static __DECLARE_SEMAPHORE_GENERIC(gnttab_sem, 0);
static void
put_free_entry(grant_ref_t ref)
{
unsigned long flags;
local_irq_save(flags);
#ifdef GNT_DEBUG
BUG_ON(!inuse[ref]);
inuse[ref] = 0;
#endif
gnttab_list[ref] = gnttab_list[0];
gnttab_list[0] = ref;
local_irq_restore(flags);
up(&gnttab_sem);
}
static grant_ref_t
get_free_entry(void)
{
unsigned int ref;
unsigned long flags;
down(&gnttab_sem);
local_irq_save(flags);
ref = gnttab_list[0];
BUG_ON(ref < NR_RESERVED_ENTRIES || ref >= NR_GRANT_ENTRIES);
gnttab_list[0] = gnttab_list[ref];
#ifdef GNT_DEBUG
BUG_ON(inuse[ref]);
inuse[ref] = 1;
#endif
local_irq_restore(flags);
return ref;
}
grant_ref_t
gnttab_grant_access(domid_t domid, unsigned long frame, int readonly)
{
grant_ref_t ref;
ref = get_free_entry();
gnttab_table[ref].frame = frame;
gnttab_table[ref].domid = domid;
wmb();
readonly *= GTF_readonly;
gnttab_table[ref].flags = GTF_permit_access | readonly;
return ref;
}
grant_ref_t
gnttab_grant_transfer(domid_t domid, unsigned long pfn)
{
grant_ref_t ref;
ref = get_free_entry();
gnttab_table[ref].frame = pfn;
gnttab_table[ref].domid = domid;
wmb();
gnttab_table[ref].flags = GTF_accept_transfer;
return ref;
}
int
gnttab_end_access(grant_ref_t ref)
{
uint16_t flags, nflags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
nflags = gnttab_table[ref].flags;
do {
if ((flags = nflags) & (GTF_reading|GTF_writing)) {
printk("WARNING: g.e. still in use! (%x)\n", flags);
return 0;
}
} while ((nflags = synch_cmpxchg(&gnttab_table[ref].flags, flags, 0)) !=
flags);
put_free_entry(ref);
return 1;
}
unsigned long
gnttab_end_transfer(grant_ref_t ref)
{
unsigned long frame;
uint16_t flags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
while (!((flags = gnttab_table[ref].flags) & GTF_transfer_committed)) {
if (synch_cmpxchg(&gnttab_table[ref].flags, flags, 0) == flags) {
printk("Release unused transfer grant.\n");
put_free_entry(ref);
return 0;
}
}
/* If a transfer is in progress then wait until it is completed. */
while (!(flags & GTF_transfer_completed)) {
flags = gnttab_table[ref].flags;
}
/* Read the frame number /after/ reading completion status. */
rmb();
frame = gnttab_table[ref].frame;
put_free_entry(ref);
return frame;
}
grant_ref_t
gnttab_alloc_and_grant(void **map)
{
unsigned long mfn;
grant_ref_t gref;
*map = (void *)alloc_page();
mfn = virt_to_mfn(*map);
gref = gnttab_grant_access(0, mfn, 0);
return gref;
}
static const char * const gnttabop_error_msgs[] = GNTTABOP_error_msgs;
const char *
gnttabop_error(int16_t status)
{
status = -status;
if (status < 0 || status >= ARRAY_SIZE(gnttabop_error_msgs))
return "bad status";
else
return gnttabop_error_msgs[status];
}
void
init_gnttab(void)
{
struct gnttab_setup_table setup;
unsigned long frames[NR_GRANT_FRAMES];
int i;
#ifdef GNT_DEBUG
memset(inuse, 1, sizeof(inuse));
#endif
for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++)
put_free_entry(i);
setup.dom = DOMID_SELF;
setup.nr_frames = NR_GRANT_FRAMES;
set_xen_guest_handle(setup.frame_list, frames);
HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
gnttab_table = map_frames(frames, NR_GRANT_FRAMES);
printk("gnttab_table mapped at %p.\n", gnttab_table);
}
void
fini_gnttab(void)
{
struct gnttab_setup_table setup;
setup.dom = DOMID_SELF;
setup.nr_frames = 0;
HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
}
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