Messages in this thread |  | | Subject | Re: [PATCH v6 13/18] KVM: arm64: Support SDEI_EVENT_{COMPLETE,COMPLETE_AND_RESUME} hypercall | From | Gavin Shan <> | Date | Mon, 2 May 2022 15:51:23 +0800 |
| |
Hi Oliver,
On 5/2/22 3:38 PM, Oliver Upton wrote: > On Mon, May 02, 2022 at 02:19:30PM +0800, Gavin Shan wrote: >> 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(). > > Right -- but look at what its doing. It returns the address at which it > wants to resume execution. > > arch/arm64/kernel.entry.S::__sdei_asm_handler winds up passing this as > an argument to COMPLETE_AND_RESUME. Also, what would happen if we run > something that isn't Linux inside of KVM? This is why I suggested > implementing COMPLETE_AND_RESUME in line with the specification, not > based on what the kernel is presently doing. >
Indeed. The address for the resumed execution is passed by x1 when COMPLETE_AND_RESUME is called. I will figure this out in next revision. I don't think we can have the assumption that the guest is linux.
Thanks again for your review and comments :)
Thanks, Gavin
|  |