Re: [Xen-devel] ipi(inter-processor interrupt) about xen hypervisor

[Tim Deegan <tim@xxxxxxx>]

Hi,

At 23:59 +0800 on 15 Feb (1360972763), zhang zhi wrote:
>          In the context of multi-core mode, core 1 is in root-mode, meaning
> that it's running VMM. And core 2 is in non-root mode, meaning that it's
> running guest OS in kernel level. If core 1 wants core2 to execute a
> pre-defined program located in kernel-mode, say a syscall or a virtual
> external interrupt handler(the program is completed via syscall or another
> kernel module). Considering that core1 is in vmm mode, and core2 is not
> supposed to vm-exit, so I can't use the method of event-delivery. What kind
> of thing should core 1 do ? 

If you need the VM on core 2 to act immediately (and it's currently
doing something other than waiting for core 1 to send it a message) then
you'll need to send it some sort of interrupt.  There's no way of doing
that in Xen without core 2 vm-exiting, because all interrupts are
handled in Xen.

In theory you could implement something like ELI for Xen.  That could be
interesting, not least as a piece of repeated research, but it's quite a
serious undertaking.
(http://researcher.watson.ibm.com/researcher/files/il-ABELG/eli_asplos12.pdf)

Of course, if you don't need an immediate answer, any shared-memory
protocol will do.  You just need to arrange for the VM to check for
messages periodically.

Cheers,

Tim.

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