From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5667C43603 for ; Thu, 12 Dec 2019 17:35:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF56B21556 for ; Thu, 12 Dec 2019 17:35:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730110AbfLLRfP (ORCPT ); Thu, 12 Dec 2019 12:35:15 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:24544 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730088AbfLLRfP (ORCPT ); Thu, 12 Dec 2019 12:35:15 -0500 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xBCHYju9053844 for ; Thu, 12 Dec 2019 12:35:14 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0b-001b2d01.pphosted.com with ESMTP id 2wu4t7edqq-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 12 Dec 2019 12:35:08 -0500 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 12 Dec 2019 17:33:16 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xBCHXF3S45285574 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 12 Dec 2019 17:33:15 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6E9ECA4054; Thu, 12 Dec 2019 17:33:15 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 36727A405B; Thu, 12 Dec 2019 17:33:15 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.152.222.89]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 12 Dec 2019 17:33:15 +0000 (GMT) Subject: Re: [kvm-unit-tests PATCH v4 7/9] s390x: css: msch, enable test From: Pierre Morel To: Cornelia Huck Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@redhat.com, thuth@redhat.com References: <1576079170-7244-1-git-send-email-pmorel@linux.ibm.com> <1576079170-7244-8-git-send-email-pmorel@linux.ibm.com> <20191212130111.0f75fe7f.cohuck@redhat.com> <83d45c31-30c3-36e1-1d68-51b88448f4af@linux.ibm.com> <20191212151002.1c7ca4eb.cohuck@redhat.com> <20191212153303.6444697e.cohuck@redhat.com> Date: Thu, 12 Dec 2019 18:33:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19121217-4275-0000-0000-0000038E56E3 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19121217-4276-0000-0000-000038A211D3 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-12_05:2019-12-12,2019-12-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 spamscore=0 clxscore=1015 suspectscore=0 mlxscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912120137 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2019-12-12 17:05, Pierre Morel wrote: > > > On 2019-12-12 15:33, Cornelia Huck wrote: >> On Thu, 12 Dec 2019 15:21:21 +0100 >> Pierre Morel wrote: >> >>> On 2019-12-12 15:10, Cornelia Huck wrote: >>>> On Thu, 12 Dec 2019 15:01:07 +0100 >>>> Pierre Morel wrote: >>>>> On 2019-12-12 13:01, Cornelia Huck wrote: >>>>>> On Wed, 11 Dec 2019 16:46:08 +0100 >>>>>> Pierre Morel wrote: >>>>>>> A second step when testing the channel subsystem is to prepare a >>>>>>> channel >>>>>>> for use. >>>>>>> This includes: >>>>>>> - Get the current SubCHannel Information Block (SCHIB) using STSCH >>>>>>> - Update it in memory to set the ENABLE bit >>>>>>> - Tell the CSS that the SCHIB has been modified using MSCH >>>>>>> - Get the SCHIB from the CSS again to verify that the subchannel is >>>>>>>      enabled. >>>>>>> >>>>>>> This tests the success of the MSCH instruction by enabling a >>>>>>> channel. >>>>>>> >>>>>>> Signed-off-by: Pierre Morel >>>>>>> --- >>>>>>>     s390x/css.c | 65 >>>>>>> +++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>>>>>     1 file changed, 65 insertions(+) >>>>>>> +    /* Read the SCHIB for this subchannel */ >>>>>>> +    cc = stsch(test_device_sid, &schib); >>>>>>> +    if (cc) { >>>>>>> +        report(0, "stsch cc=%d", cc); >>>>>>> +        return; >>>>>>> +    } >>>>>>> + >>>>>>> +    /* Update the SCHIB to enable the channel */ >>>>>>> +    pmcw->flags |= PMCW_ENABLE; >>>>>>> + >>>>>>> +    /* Tell the CSS we want to modify the subchannel */ >>>>>>> +    cc = msch(test_device_sid, &schib); >>>>>>> +    if (cc) { >>>>>>> +        /* >>>>>>> +         * If the subchannel is status pending or >>>>>>> +         * if a function is in progress, >>>>>>> +         * we consider both cases as errors. >>>>>>> +         */ >>>>>>> +        report(0, "msch cc=%d", cc); >>>>>>> +        return; >>>>>>> +    } >>>>>>> + >>>>>>> +    /* >>>>>>> +     * Read the SCHIB again to verify the enablement >>>>>>> +     * insert a little delay and try 5 times. >>>>>>> +     */ >>>>>>> +    do { >>>>>>> +        cc = stsch(test_device_sid, &schib); >>>>>>> +        if (cc) { >>>>>>> +            report(0, "stsch cc=%d", cc); >>>>>>> +            return; >>>>>>> +        } >>>>>>> +        delay(10); >>>>>> >>>>>> That's just a short delay to avoid a busy loop, right? msch should be >>>>>> immediate, >>>>> >>>>> Thought you told to me that it may not be immediate in zVM did I >>>>> misunderstand? >>>> >>>> Maybe I have been confusing... what I'm referring to is this >>>> programming note for msch: >>>> >>>> "It is recommended that the program inspect the >>>> contents of the subchannel by subsequently >>>> issuing STORE SUBCHANNEL when MODIFY >>>> SUBCHANNEL sets condition code 0. Use of >>>> STORE SUBCHANNEL is a method for deter- >>>> mining if the designated subchannel was >>>> changed or not. Failure to inspect the subchan- >>>> nel following the setting of condition code 0 by >>>> MODIFY SUBCHANNEL may result in conditions >>>> that the program does not expect to occur." >>>> >>>> That's exactly what we had to do under z/VM back then: do the msch, >>>> check via stsch, redo the msch if needed, check again via stsch. It >>>> usually worked with the second msch the latest. >>> >>> OK, I understand, then it is a bug in zVM that this test could >>> enlighten. >> >> Probably more a quirk than a bug... the explanation there is not >> explicit about that :) >> >>> >>> I think we should keep it so, it allows to recognize 3 cases (after I >>> change to test ENABLE in the loop as I said I will): >>> - immediate ENABLE >> >> This is the good case. >> >>> - asynchrone ENABLE >> >> This one I would consider an architecture violation. >> >>> - failure to ENABLE >> >> This is the quirk above. >> >> But I'm not quite sure how you would be able to distinguish the last >> two cases? > > This is where the delay can help. > But yes, not sure that we can differentiate this without to know how > long we should delay. > > >> >>>>>> and you probably should not delay on success? >>>>> >>>>> yes, it is not optimized, I can test PMCW_ENABLE in the loop this >>>>> way we >>>>> can see if, in the zVM case we need to do retries or not. >>>>> >>>>>>> +    } while (!(pmcw->flags & PMCW_ENABLE) && count++ < 5); >>>>>> >>>>>> How is this supposed to work? Doesn't the stsch overwrite the control >>>>>> block again, so you need to re-set the enable bit before you retry? >>>>> >>>>> I do not think so, there is no msch() in the loop. >>>>> Do I miss something? >>>> >>>> Well, _I_ missed that the msch() was missing :) You need it (see >>>> above); >>>> just waiting and re-doing the stsch is useless, as msch is a >>>> synchronous instruction which has finished its processing after the cc >>>> has been set. >>> >>> Since kvm-unit-test is a test system, not an OS so I think that here we >>> have one more point to leverage the enable function: >>> - We need to test the enable (what I did (partially)) >> >> Maybe also log if you needed to retry? Not as an error, but as >> additional information? > > Yes. > > Regards, > Pierre > After all, I make it simple by testing if the MSCH works as expected, no retry, no delay. This is just a test. I will add a new patch to add a library function to enable the channel, with retry to serve when we really need to enable the channel, not to test. Regards, Pierre -- Pierre Morel IBM Lab Boeblingen