Hi.
I want to share some pages between Dom0 and
DomU.
But I have some problems with it.
The sharing scenario is like that.
1.
Dom0 grants access permission
of pages to DomU using “gnttab_grant_foreign_access_ref()”
2.
Dom0 passes “Machine Page
Numbers” and “Ref” to DomU through I/O Ring
3.
DomU install granted pages. (Change
original mfn to new mfn of Dom0)
A.
map.host_addr =
mfn_to_virt(pfn_to_mfn(DomU’s PFN));
B.
HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,&map,count)
C.
Set_phys_to_machine(DomU’s
PFN, Dom0’s MFN)
They are being done in “blkback.c”
and “blkfront.c”.
The source code is
In blkback.c
dom0_cache_vaddr
= get_zeroed_page(GFP_KERNEL);
dom0_cache_mfn[i]
= pfn_to_mfn(__pa(dom0_cache_vaddr) >> PAGE_SHIFT);
share_ref =
gnttab_claim_grant_reference(&share_ref_head);
BUG_ON(share_ref
== -ENOSPC);
share_ref
= gnttab_grant_foreign_access( req_domid, dom0_cache_mfn[i], 1);
In blkfront.c
bret
= RING_GET_RESPONSE(&info->ring, i);
map.host_addr
= mfn_to_virt(pfn_to_mfn(bret->map_pfn_mfn[j].pfn));
for(j < 0 ; j
< number_of_pages ;j++){
map.dom
= (domid_t) 0;
map.ref
= bret->map_pfn_mfn[j].ref;
map.flags
= ( GNTMAP_host_map | GNTMAP_readonly);
ret
= HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,&map,1);
BUG_ON(ret);
set_phys_to_machine(
bret->map_pfn_mfn[j].pfn,
FOREIGN_FRAME((bret->map_pfn_mfn[j].mfn)));
}
For the sharing, I modified response
struct. So it has grant ref, Dom0’s MFN and DomU’s PFN now.
But I encountered Kernel Panic as DomU booted
up.
Message :
Unable to handle
kernel paging request at virtual address c0cff000
printing
eip:
c0148bc1
*pde = ma
1d639067 pa 0116a067
*pte = ma
0db4f061 pa 10b4f061
Question :
1.
Should I update Page table with
“HYPERVISOR_mmu_update” in DomU although I call “HYPERVISOR_grant_table_op”??
2.
Anyone can advice to me about
this problem? (Anything about the kernel panic message or mistakes in source
code)
Thank you very much. :-)
