Dear All,
I am doing a small experiment with grant table to share 4 pages of
memory between 2 miniOS, but have not been successful. For some reason,
my GNTTABOP_map_grant_ref returns -1, and the 2 miniOS does not see the
same machine address.
I have attached here the code for the two threads i created for DomA and
DomB respectively, as well as their output. Please, suggest what i
should change here.
I will appreciate too if you can point me to a pointer that explains
grant tables with some example code.
Thank you for your reply in advance,
-- Lamia Youseff
/******************************************************************************
* kernel.c - mini-Os-grnt-garntee (Dom A. domid = 30)
*******************************************************************************/
void UCSB_grantee_thread(void *p)
{
grant_ref_t gref[1]; // each grant_ref_t should provide me with 4k of
shared memory
void **map;
char mystring[30]="Welcome to Shared Memory.\n";
unsigned long mfn;
*map = (void *) alloc_pages(2);
memcpy(*map, mystring, 30);
// get the machine physical address of the domain
mfn = virt_to_mfn(*map);
// now, share the page with remote domain (say dom 31)
gref[0] = gnttab_grant_access( 31, //domid
mfn, // the page to be shared
0 ); // i.e. 0 == rw. 1 == ro.
printk("My machine address is %u\n", virt_to_mach(*map));
printk("My grant_ref_t is %d.\n", (unsigned int) gref[0]);
// now sleep till the other domain access the page
for (;;){
sleep(1000);
}
return;
}
/******************************************************************************
* kernel.c -- mini-Os-grnt-garnted (i.e. DomB, domid = 31)
*
****************************************************************************/
void UCSB_granted_thread(void *p)
{
unsigned long vm_area;
int error_val;
gnttab_map_grant_ref_t aop[1];
grant_handle_t ghandle[1];
int i;
grant_ref_t gref[1];
gref[0] = 8;
vm_area = (unsigned long) alloc_pages(4);
aop[0].host_addr = vm_area;
aop[0].dom = 30; // domAid;
aop[0].ref = gref[0];
aop[0].flags = ( GNTMAP_host_map | GNTMAP_readonly );
error_val = HYPERVISOR_grant_table_op( GNTTABOP_map_grant_ref, aop, 1);
printk("My machine address is %u\n", virt_to_mach(vm_area));
printk("Error in granting_op in (HYPERVISOR_grant_table_o). Error
%d....%d\n", aop[0].status, error_val);
printk("Error ==> %s\n", gnttabop_error(aop[0].status));
if (aop[0].status != GNTST_okay){
printk("Error in the return status for GNTTAB_entry %d\n", i);
return;
}
if ( unlikely(aop[0].handle < 0) ){
printk("Error in aop[0].handle\n");
return;
}
else ghandle[0]= aop[0].handle;
printk("My string is %s\n", (char *) vm_area);
return ;
}
/**************************************************
* Output from DomA
**************************************************/
Started domain Mini-OS-grantee
Xen Minimal OS!
start_info: 0001f000
nr_pages: 8192 shared_inf: 001af000
pt_base: 00022000 mod_start: 0x0
mod_len: 0
flags: 0x0
stack: 000140e0-000160e0
MM: Init
_text: 00000000
_etext: 0000b19a
_edata: 0000c7a0
stack start: 000140e0
_end: 00016534
start_pfn: 2a
max_pfn: 2000
Mapping memory range 0x400000 - 0x2000000
MM: Initialise page allocator for 38000(38000)-2000000(2000000)
MM: done
Demand map pfns start at 2200 (02200000).
Initialised demand area.
Initialising timer interface
Initialising console ... done.
gnttab_table mapped at 02200000.
Initialising scheduler
Thread "Idle": pointer: 0x3a00c, stack: 0x3c000
Initialising xenbus
Thread "xenstore": pointer: 0x3a03c, stack: 0x3e000
Dummy main: start_info=000160e0
Thread "xenbus_tester": pointer: 0x3a06c, stack: 0x40000
Thread "UCSB_grantee_thread": pointer: 0x3a09c, stack: 0x42000
Xenbus tests disabled, because of a Xend bug.
Thread "xenbus_tester" exited.
My machine address is 979255296
My grant_ref_t is 8.
/**************************************************
* Output from DomB
**************************************************/
Started domain Mini-OS-granted
Xen Minimal OS!
start_info: 0001f000
nr_pages: 8192 shared_inf: 001a9000
pt_base: 00022000 mod_start: 0x0
mod_len: 0
flags: 0x0
cmd_line:
stack: 00014180-00016180
MM: Init
_text: 00000000
_etext: 0000b1ce
_edata: 0000c840
stack start: 00014180
_end: 000165d4
start_pfn: 2a
max_pfn: 2000
Mapping memory range 0x400000 - 0x2000000
MM: Initialise page allocator for 38000(38000)-2000000(2000000)
MM: done
Demand map pfns start at 2200 (02200000).
Initialised demand area.
Initialising timer interface
Initialising console ... done.
gnttab_table mapped at 02200000.
Initialising scheduler
Thread "Idle": pointer: 0x3a00c, stack: 0x3c000
Initialising xenbus
Thread "xenstore": pointer: 0x3a03c, stack: 0x3e000
Dummy main: start_info=00016180
Thread "xenbus_tester": pointer: 0x3a06c, stack: 0x40000
Thread "UCSB_granted_thread": pointer: 0x3a09c, stack: 0x42000
Xenbus tests disabled, because of a Xend bug.
Thread "xenbus_tester" exited.
My machine address is 200548352
Error in granting_op in (HYPERVISOR_grant_table_o). Error 0....-1
Error ==> okay
My string is
My string is
Thread "UCSB_granted_thread" exited.
[$$]# xm list
Name ID Mem VCPUs State
Time(s)
Domain-0 0 256 1 r----- 1120.0
Mini-OS-granted 31 32 1 -b---- 0.0
Mini-OS-grantee 30 32 1 -b---- 0.0
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