Hi
The following patches introduce and implement grant table version
2, and they are based on v3.1.0-rc9+.
Descriptions for those patches:
1. In those patches, the grant table code supports both grant
table v1 and v2 version, v2 is an extension from v1. Grant table
of guest domain can be either v1 or v2 version, and every grant
table entry on one guest should be the same version.
2. Full page structure of grant table v2 play the same role as
grant table v1. Although full page structure is different from v1,
grant table 2 is totally backwards compatible with v1. Grant table
is shared between guest and Xen, domu and dom0 all have their own
grant table shared with Xen, and their grant table version should
be set before any grants are activated. When domu grants an entry
to dom0 to map a frame, following are steps:
* domu introduces a grant entry by reference
* domu informs dom0 the gref
* dom0 sends hypercall to map frame through this reference, Xen
copy shared entry to active entry and update frame
* dom0 does its work and release the frame, Xen releases the
entry.
* domu redo those steps for a new cycle.
Xen mapping process can be found in function
__gnttab_map_grant_ref in link:
http://xenbits.xen.org/hg/xen-4.1-testing.hg/file/81e39a4978ea/xen/common/grant_table.c#l2172
3. If dom0 supports grant table v2, guests run on it can either
supports v1 or v2. Xen is responsible to judge what version the
guests are using. This is implemented in link:
http://xenbits.xen.org/hg/xen-4.1-testing.hg/file/81e39a4978ea/xen/common/grant_table.c#l2172.
Key word is: rd->grant_table->gt_version.
4. Grant table2 is a precondition to netchannel2 mechanism.
Netchannel2 imports a new device type: vif2. To support this type,
we need new netback2, netfront2 driver and modification in Xen. If
all are ready, two types of vif can be supported: vif and vif2.
vif is for original backend and frontend, vif2 is for netback2 and
netfront2.
Thanks
Annie
Home