[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Ideas for PV on SeaBIOS
On Thu, 2011-05-19 at 08:19 +0100, Keir Fraser wrote: > On 19/05/2011 06:33, "Daniel Castro" <evil.dani@xxxxxxxxx> wrote: > > > Good Day, > > > > In order to give PV Drivers to SeaBIOS we will need to solve a few > > problems, one is the following: > > Does a booting kernel informs the BIOS that it will leave real mode > > and not use it again? When the booting kernel uses CPU real mode for > > the last time, how can we (Xen or SeaBIOS) know that real mode will no > > longer be used, and hence BIOS calls will not be issued? > > We want upon last real mode usage to leave all Xen PV information in a > > clean state, this means, closing the channel and ring between the > > newly created domain and the host system. > > > > If you have any ideas please let me know. > > There's no easy way. Best effort might be to hook off the guest OS setting > up its PV drivers. One of the first steps of that would be getting a > hypercall transfer page, and also setting up event-channel delivery. Probably the first thing it will do is hit the Xen CPUID leaf. > It may > be necessary for the hypervisor to give the BIOS some help by delivering a > pre-registered callback on one of those events, to clean up. This is made > uglier by the fact you don't know what execution mode the OS might be in > when it triggers the callback. Virtual SMM? :-( > Needs a bit more thought. We had a bit of a brainstorm yesterday and someone suggested that perhaps qemu could deal with it when it sees the I/O ports for the emulated device unplug get hit. That would potentially mean communicating a bunch of frontend state to qemu though, which could get pretty ugly. More thought indeed. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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