Re: [PATCH v12 2/6] x86/ioreq server: Add DMOP to map guest ram with p2m_ioreq_server to an ioreq server.

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Yu Zhang [mailto:yu.c.zhang@linux.intel.com]
> Sent: Thursday, April 6, 2017 11:54 PM
> 
> Previously, p2m_ioreq_server is used to write-protect guest ram
> pages, which are tracked with ioreq server's rangeset. However,
> number of ram pages to be tracked may exceed the upper limit of
> rangeset.
> 
> Now, a new DMOP - XEN_DMOP_map_mem_type_to_ioreq_server, is added
> to let one ioreq server claim/disclaim its responsibility for the
> handling of guest pages with p2m type p2m_ioreq_server. Users of
> this DMOP can specify which kind of operation is supposed to be
> emulated in a parameter named flags. Currently, this DMOP only
> support the emulation of write operations. And it can be further
> extended to support the emulation of read ones if an ioreq server
> has such requirement in the future.
> 
> For now, we only support one ioreq server for this p2m type, so
> once an ioreq server has claimed its ownership, subsequent calls
> of the XEN_DMOP_map_mem_type_to_ioreq_server will fail. Users can
> also disclaim the ownership of guest ram pages with p2m_ioreq_server,
> by triggering this new DMOP, with ioreq server id set to the current
> owner's and flags parameter set to 0.
> 
> Note:
> a> both XEN_DMOP_map_mem_type_to_ioreq_server and
> p2m_ioreq_server
> are only supported for HVMs with HAP enabled.
> 
> b> only after one ioreq server claims its ownership of p2m_ioreq_server,
> will the p2m type change to p2m_ioreq_server be allowed.
> 
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> Acked-by: Tim Deegan <tim@xen.org>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> Reviewed-by: George Dunlap <george.dunlap@citrix.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

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