Messages in this thread | | | Subject | Re: [PATCH] zcrypt: handle AP Info notification from CHSC SEI command | From | Tony Krowiak <> | Date | Fri, 1 Feb 2019 10:50:13 -0500 |
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On 2/1/19 9:35 AM, Cornelia Huck wrote: > On Thu, 31 Jan 2019 18:50:57 -0500 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> On 1/31/19 4:55 AM, Cornelia Huck wrote: >>> On Wed, 30 Jan 2019 12:48:46 -0500 >>> Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >>> Two questions: >>> - Does the event cover _any_ change to the AP configuration, or can the >>> periodic scan detect changes that are not signaled? >> >> It can detect any change, such as a change to the CRYCB masks. > > Nice. I suppose we can not rely on those messages being generated, > though, and therefore need to keep the periodic scan...
I don't know how the CRYCB can be changed dynamically on the host, but hot plug for a guest changes it dynamically. Down the road, we may send a CHSC SEI AP Configuration event to let the guest know. I don't know if there may be other AP config changes that can occur without this event being posted, so it is probably a good idea to keep the scan. It certainly doesn't hurt anything to do so.
> >> >>> - Do we want to generate such an event in QEMU on plugging/unplugging >>> the vfio-ap device? >> >> We've discussed this quite a bit internally and decided not to implement >> that at this time. We will address it as a future enhancement. > > Ok, but I think it would be nice to have.
Duly noted, but that discussion is outside of scope for this patch.
> >>>> diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c >>>> index a0baee25134c..dccccc337078 100644 >>>> --- a/drivers/s390/cio/chsc.c >>>> +++ b/drivers/s390/cio/chsc.c >>>> @@ -586,6 +586,15 @@ static void chsc_process_sei_scm_avail(struct chsc_sei_nt0_area *sei_area) >>>> " failed (rc=%d).\n", ret); >>>> } >>>> >>>> +static void chsc_process_sei_ap_cfg_chg(struct chsc_sei_nt0_area *sei_area) >>>> +{ >>>> + CIO_CRW_EVENT(3, "chsc: ap config changed\n"); >>>> + if (sei_area->rs != 5) >>>> + return; >>> >>> I'm guessing that a reporting source of 5 means ap, right? (The code is >>> silent on all those magic rs values :/) >> >> The 5 indicates the accessibility of one or more adjunct processors has >> changed. The reason this gets called is because the CC sent with the >> instruction indicates the AP configuration has changed, so the reporting >> belongs where it is. There is only one RS associated with it. > > So if we'd ever get there anything but rs == 5, it would be a hardware > or hypervisor bug? Then the code makes sense, I guess.
I have no idea if that is possible, but this follows the architecture.
> >> >>> >>> If so, should the debug logging be moved after the check? >> >> covered in the response above. >> >>> >>>> + >>>> + ap_bus_cfg_chg(); >>>> +} >>>> + >
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