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// SPDX-License-Identifier: GPL-2.0
/*
* (C) 2006 - Cambridge University
* (C) 2020 - EPAM Systems Inc.
*
* File: gnttab.c [1]
* Author: Steven Smith (sos22@cam.ac.uk)
* Changes: Grzegorz Milos (gm281@cam.ac.uk)
*
* Date: July 2006
*
* Description: Simple grant tables implementation. About as stupid as it's
* possible to be and still work.
*
* [1] - http://xenbits.xen.org/gitweb/?p=mini-os.git;a=summary
*/
#include <common.h>
#include <linux/compiler.h>
#include <log.h>
#include <malloc.h>
#include <asm/armv8/mmu.h>
#include <asm/io.h>
#include <asm/xen/system.h>
#include <linux/bug.h>
#include <xen/gnttab.h>
#include <xen/hvm.h>
#include <xen/interface/memory.h>
DECLARE_GLOBAL_DATA_PTR;
#define NR_RESERVED_ENTRIES 8
/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
#define NR_GRANT_FRAMES 1
#define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * PAGE_SIZE / sizeof(struct grant_entry_v1))
static struct grant_entry_v1 *gnttab_table;
static grant_ref_t gnttab_list[NR_GRANT_ENTRIES];
static void put_free_entry(grant_ref_t ref)
{
unsigned long flags;
local_irq_save(flags);
gnttab_list[ref] = gnttab_list[0];
gnttab_list[0] = ref;
local_irq_restore(flags);
}
static grant_ref_t get_free_entry(void)
{
unsigned int ref;
unsigned long flags;
local_irq_save(flags);
ref = gnttab_list[0];
BUG_ON(ref < NR_RESERVED_ENTRIES || ref >= NR_GRANT_ENTRIES);
gnttab_list[0] = gnttab_list[ref];
local_irq_restore(flags);
return ref;
}
/**
* gnttab_grant_access() - Allow access to the given frame.
* The function creates an entry in the grant table according
* to the specified parameters.
* @domid: the id of the domain for which access is allowed
* @frame: the number of the shared frame
* @readonly: determines whether the frame is shared read-only or read-write
*
* Return: relevant grant reference
*/
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;
}
/**
* gnttab_end_access() - End of memory sharing. The function invalidates
* the entry in the grant table.
*/
int gnttab_end_access(grant_ref_t ref)
{
u16 flags, nflags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
nflags = gnttab_table[ref].flags;
do {
flags = nflags;
if ((flags) & (GTF_reading | GTF_writing)) {
printf("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;
}
grant_ref_t gnttab_alloc_and_grant(void **map)
{
unsigned long mfn;
grant_ref_t gref;
*map = (void *)memalign(PAGE_SIZE, PAGE_SIZE);
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];
}
/* Get Xen's suggested physical page assignments for the grant table. */
void get_gnttab_base(phys_addr_t *gnttab_base, phys_size_t *gnttab_sz)
{
const void *blob = gd->fdt_blob;
struct fdt_resource res;
int mem;
mem = fdt_node_offset_by_compatible(blob, -1, "xen,xen");
if (mem < 0) {
printf("No xen,xen compatible found\n");
BUG();
}
mem = fdt_get_resource(blob, mem, "reg", 0, &res);
if (mem == -FDT_ERR_NOTFOUND) {
printf("No grant table base in the device tree\n");
BUG();
}
*gnttab_base = (phys_addr_t)res.start;
if (gnttab_sz)
*gnttab_sz = (phys_size_t)(res.end - res.start + 1);
debug("FDT suggests grant table base at %llx\n",
*gnttab_base);
}
void init_gnttab(void)
{
struct xen_add_to_physmap xatp;
struct gnttab_setup_table setup;
xen_pfn_t frames[NR_GRANT_FRAMES];
int i, rc;
debug("%s\n", __func__);
for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++)
put_free_entry(i);
get_gnttab_base((phys_addr_t *)&gnttab_table, NULL);
for (i = 0; i < NR_GRANT_FRAMES; i++) {
xatp.domid = DOMID_SELF;
xatp.size = 0;
xatp.space = XENMAPSPACE_grant_table;
xatp.idx = i;
xatp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
if (rc)
printf("XENMEM_add_to_physmap failed; status = %d\n",
rc);
BUG_ON(rc != 0);
}
setup.dom = DOMID_SELF;
setup.nr_frames = NR_GRANT_FRAMES;
set_xen_guest_handle(setup.frame_list, frames);
}
void fini_gnttab(void)
{
struct xen_remove_from_physmap xrtp;
struct gnttab_setup_table setup;
int i, rc;
debug("%s\n", __func__);
for (i = 0; i < NR_GRANT_FRAMES; i++) {
xrtp.domid = DOMID_SELF;
xrtp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrtp);
if (rc)
printf("XENMEM_remove_from_physmap failed; status = %d\n",
rc);
BUG_ON(rc != 0);
}
setup.dom = DOMID_SELF;
setup.nr_frames = 0;
}
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