Re: [PATCH v6 13/18] KVM: arm64: Support SDEI_EVENT_{COMPLETE,COMPLETE_AND_RESUME} hypercall

[Gavin Shan]

Hi Oliver,

On 5/1/22 2:50 PM, Oliver Upton wrote:
> On Sun, Apr 03, 2022 at 11:39:06PM +0800, Gavin Shan wrote:
> > This supports SDEI_EVENT_{COMPLETE, COMPLETE_AND_RESUME} hypercall.
> > They are used by guest to notify the completion of event in its
> > handler. The previously interrupted or preempted context is restored
> > like below.
> >
> >     * x0 - x17, PC and PState are restored to what values we had in
> >       the interrupted or preempted context.
> >
> >     * If it's SDEI_EVENT_COMPLETE_AND_RESUME hypercall, IRQ exception
> >       is injected.
>
> I don't think that's how COMPLETE_AND_RESUME works. The caller specifies an
> address at which it would like to begin execution within the client
> exception level.
>
> SDEI spec suggests this behaves like a synchronous exception. DEN 0054C
> 5.2.2 'Event Resume Context' speaks more about how it is supposed to
> work.

It's actually the linux convention. If the event handler, which was
specified in previous hypercall to EVENT_REGISTER, returns success,
the (linux) client calls into COMPLETE_AND_RESUME and the resume
address is specified with FIQ vector offset. More details can be
found from arch/arm64/kernel::sdei.c::do_sdei_event().

Thanks,
Gavin