On 29/05/2019 09:45, Jan Beulich wrote: >>>> On 29.05.19 at 06:10, <andrew.coop...@citrix.com> wrote: >> This also introduced the top-level Guest Documentation section. >> >> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com> > Acked-by: Jan Beulich <jbeul...@suse.com>
Thanks. > with one further remark / question: > >> +Hypercall Page >> +============== >> + >> +The hypercall page is a page of guest RAM into which Xen will write suitable >> +transfer stubs. >> + >> +Creating a hypercall page is an isolated operation from Xen's point of view. >> +It is the guests responsibility to ensure that the hypercall page, once >> +written by Xen, is mapped with executable permissions so it may be used. >> +Multiple hypercall pages may be created by the guest, if it wishes. >> + >> +The stubs are arranged by hypercall index, and start on 32-byte boundaries. >> +To invoke a specific hypercall, ``call`` the relevant stub [3]_: >> + >> +.. code-block:: none >> + >> + call hypercall_page + index * 32 >> + >> +There result is an ABI which is invariant of the exact operating mode or >> +hardware vendor. This is intended to simplify guest kernel interfaces by >> +abstracting away the details of how it is currently running. > Is it worth mentioning here that certain aspects of the hypervisor interface > (shared data structures) are influenced by the mode the guest is in at the > time the most recent hypercall page registration (oddly enough alternatively > the most recent setting of HVM_PARAM_CALLBACK_IRQ) has occurred? That aspect had crossed my mind, but I decided to leave it for now. Details on the format of the shared_info page should live primarily in the shared_info documentation, but I do intend to cross reference appropriate documentation when both sides are in place. I'd prefer that any addition to this document happens when the main shared_info documentation is done, rather than having an unqualified fraction of the end result. Note however that I am taking this opportunity to evaluate the current behaviour of the areas being documented (hence the cleanup patches), and I make no guarantees that the details of shared_info latching will be identical to how they currently are, when the documentation is eventually complete. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
