From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v4 1/7] s390: ap: kvm: add PQAP interception for AQIC Date: Fri, 1 Mar 2019 16:32:30 +0100 Message-ID: <7fab18c4-9781-b776-5fd9-250ba19cafe5@linux.ibm.com> References: <1550849400-27152-1-git-send-email-pmorel@linux.ibm.com> <1550849400-27152-2-git-send-email-pmorel@linux.ibm.com> <9f1d9241-39b9-adbc-d0e9-cb702e609cbc@linux.ibm.com> <4dc59125-7f96-cba8-651b-382ed8f8bff8@linux.ibm.com> <8526f468-9a4d-68d2-3868-0dad5ce16f46@linux.ibm.com> <6058a017-6404-af3c-62ef-2452214ac97c@de.ibm.com> <2391adc2-6611-034c-61c5-feb46e2a751b@de.ibm.com> <20190228122251.75b31f62.cohuck@redhat.com> <20190228145254.2909425e.cohuck@redhat.com> <261a1e22-3703-21a4-e33d-e737651e7d89@linux.ibm.com> <3fedbde5-ef83-c67e-6352-fd492f258009@linux.ibm.com> <20190301133609.3ee469dc.cohuck@redhat.com> Reply-To: pmorel@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190301133609.3ee469dc.cohuck@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck , Christian Borntraeger Cc: Tony Krowiak , alex.williamson@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com List-ID: On 01/03/2019 13:36, Cornelia Huck wrote: > On Fri, 1 Mar 2019 13:05:54 +0100 > Christian Borntraeger wrote: > >> On 01.03.2019 13:03, Pierre Morel wrote: >>> On 28/02/2019 15:14, Pierre Morel wrote: >>>> On 28/02/2019 14:52, Cornelia Huck wrote: >>>>> On Thu, 28 Feb 2019 14:16:09 +0100 >>>>> Pierre Morel wrote: >>>>> >>>>>> On 28/02/2019 12:22, Cornelia Huck wrote: >>>>> >>>>>>> So, to summarize, the function should do: >>>>>>> - Is userspace supposed to emulate everything (!ECA_APIE)? Return >>>>>>>     -EOPNOTSUPP to hand control to it. >>>>>>> - We are now interpreting the instruction in KVM. Do common checks >>>>>>>     (PSTATE etc.) and inject exceptions, if needed. >>>>>>> - Now look at the fc; if there's a handler for it, call that; if not >>>>>>>     (case does not attempt to call a specific handler, or no handler >>>>>>>     registered), inject a specification exception. (Do we want pre-checks >>>>>>>     like for facility 65 here, or in the handler?) >>>>>>> >>>>>>> That response code 0x01 thingy probably needs to go into the specific >>>>>>> handler function, if anywhere (don't know the semantics, sorry). >>>>>> >>>>>> What do you mean with specific handler function? >>>>>> >>>>>> If you mean a switch around the FC with static function's call, I agree, >>>>>> if you mean a jump into a hook I do not agree. >>>>> >>>>> Ah, ok; so each case (that we want to handle) should call into a >>>>> subhandler that does >>>>> { >>>>>     (... check things like facilities ...) >>>>>     if (!specific_hook) >>>>>         inject_specif_excp_and_return(); >>>>>     ret = specific_hook(); >>>>>     if (ret) >>>>>         set_resp_code_0x01(); // or in specific_hook()? >>>>> } >>>>> >>>>> ? >>>> >>>> Yes something in this direction. >>> >>> Sorry, after reflection, no, we do not want to change the previous behavior so we only handle the AQIC case. >> >> I think what you wanted to say is the following: >> Today (without the patch set) we will answer PQAP with an exception. >> With this patch set we want to handle FC==3, but nothing else. So for anything FC!=3 we >> will continue to return an exception? >> >> Correct? Yes correct. Thanks for the much preciser explanation. >> > > That sounds reasonable; but I don't see how this conflicts with my > proposal? Just don't introduce a subfunction for fc != 3... > Correct too, it does not conflict, as you said it is just not introduce subfunctions. Regards, Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany