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Mon, 7 Dec 2020 20:13:27 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 173107805E; Mon, 7 Dec 2020 20:13:26 +0000 (GMT) Received: from localhost.localdomain (unknown [9.85.174.71]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 7 Dec 2020 20:13:26 +0000 (GMT) Subject: Re: [PATCH v4] self_tests/kvm: sync_regs test for diag318 To: Christian Borntraeger , kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: frankja@linux.ibm.com, david@redhat.com, thuth@redhat.com, cohuck@redhat.com, pbonzini@redhat.com, imbrenda@linux.ibm.com References: <20201207154125.10322-1-walling@linux.ibm.com> <2ea47a0e-40fb-35bc-5819-63a9e7b2ec59@de.ibm.com> <87bf5fb7-26bf-f757-1efa-d2a49bde5188@de.ibm.com> From: Collin Walling Message-ID: <501fe03a-c245-73f3-4715-1327cc73a712@linux.ibm.com> Date: Mon, 7 Dec 2020 15:13:26 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <87bf5fb7-26bf-f757-1efa-d2a49bde5188@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-07_16:2020-12-04,2020-12-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 clxscore=1015 mlxlogscore=999 lowpriorityscore=0 suspectscore=0 spamscore=0 malwarescore=0 bulkscore=0 mlxscore=0 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012070125 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 12/7/20 3:09 PM, Christian Borntraeger wrote: > > > On 07.12.20 21:06, Collin Walling wrote: >> On 12/7/20 2:32 PM, Christian Borntraeger wrote: >>> On 07.12.20 16:41, Collin Walling wrote: >>>> The DIAGNOSE 0x0318 instruction, unique to s390x, is a privileged call >>>> that must be intercepted via SIE, handled in userspace, and the >>>> information set by the instruction is communicated back to KVM. >>>> >>>> To test the instruction interception, an ad-hoc handler is defined which >>>> simply has a VM execute the instruction and then userspace will extract >>>> the necessary info. The handler is defined such that the instruction >>>> invocation occurs only once. It is up to the caller to determine how the >>>> info returned by this handler should be used. >>>> >>>> The diag318 info is communicated from userspace to KVM via a sync_regs >>>> call. This is tested During a sync_regs test, where the diag318 info is >>>> requested via the handler, then the info is stored in the appropriate >>>> register in KVM via a sync registers call. >>>> >>>> If KVM does not support diag318, then the tests will print a message >>>> stating that diag318 was skipped, and the asserts will simply test >>>> against a value of 0. >>>> >>>> Signed-off-by: Collin Walling >>> >>> Interestingly enough, this testcase actually trigger a bug: >>> While we gracefully handle this (no crash) >>> debugfs: Directory 'kvm-200206' with parent 's390dbf' already present! >>> is certainly not ideal.... >>> >> >> Odd... I wonder what triggered this behavior? >> >> I run my tests with a simple command: >> >> make summary=0 TARGETS=kvm kselftest >> >> This must have something to do with spinning up another VM to get the >> diag318 data. I think if I have the sync_regs test call the diag handler >> first, and then have the sync regs create a VM, that might solve that >> issue... > > Yes, the s390dbf code will try to create a file named kvm-%pid. With > 2 VMs the 2nd one fails. Luckily the kvm will be created anyway and > also the shutdown seems to be fine, still.... > >> >> May I ask how you encountered this bug so I may replicate in on my end? > > I just did > make TARGETS=kvm selftests > > and then the error is on dmesg. > Thanks. v5 with fix incoming. -- Regards, Collin Stay safe and stay healthy