Re: Crashing kernel with dom0/libxc gnttab/gntshr

[David Vrabel <david.vrabel@citrix.com>]

On 30/07/13 16:50, Vincent Bernardoff wrote:
> I also have a bug using tools/libvchan/vchan-node1:
> 
> When killing the server node (sudo ./vchan-node1 server read 0
> /local/domain/0/vchan) before the client node (sudo ./vchan-node1 client
> write 0 /local/domain/0/vchan), the following dmesg error appears.

Does this only happen if both client and server are in the same domain?
 Have you tested it using two domains? Did it work?

> I'm using Xen unstable (master branch) and stock Archlinux 3.10.3-1-ARCH
> kernel.
> 
> Use the following script (setup.sh) if you want to try reproducing it
> with vchan-node1, vchan-node1 indeed needs some xenstore keys to be
> written in order to work correctly.

[  902.729307] BUG: Bad page map in process vchan-node1  pte:12bfff167
pmd:b9b5c067
[  902.729312] page:ffffea0004afffc0 count:1 mapcount:-1 mapping:
   (null) index:0xffffffffffffffff

I think this is the test for page_mapcount(page) < 0 in zap_pte_range().
 This has looked up the page using the PTE it is trying to clear.  Has
it found the correct page?  Since the MFN is currently mapped into the
same domain, has the m2p_override stuff confused the look up and it is
checking the grantee page not the granter?

David