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. :-)