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Tue, 21 Jan 2020 14:33:04 +0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08026.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 00LEX3G336503820 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 21 Jan 2020 14:33:03 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3D439C6057; Tue, 21 Jan 2020 14:33:03 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9549CC6055; Tue, 21 Jan 2020 14:33:02 +0000 (GMT) Received: from oc4221205838.ibm.com (unknown [9.85.144.147]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 21 Jan 2020 14:33:02 +0000 (GMT) Subject: Re: [PATCH v3] target/s390x/kvm: Enable adapter interruption suppression again To: Cornelia Huck , Thomas Huth References: <20200120132441.11884-1-thuth@redhat.com> <20200120182747.5135fea8.cohuck@redhat.com> From: Matthew Rosato Message-ID: <95fa3c7d-8879-1401-6847-c5fa82a0cd3c@linux.ibm.com> Date: Tue, 21 Jan 2020 09:33:02 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20200120182747.5135fea8.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-01-21_04:2020-01-21, 2020-01-21 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 suspectscore=0 bulkscore=0 phishscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 malwarescore=0 mlxlogscore=999 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001210120 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, qemu-devel@nongnu.org, David Hildenbrand Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/20/20 12:27 PM, Cornelia Huck wrote: > On Mon, 20 Jan 2020 14:24:41 +0100 > Thomas Huth wrote: > >> The AIS feature has been disabled late in the v2.10 development cycle since >> there were some issues with migration (see commit 3f2d07b3b01ea61126b - >> "s390x/ais: for 2.10 stable: disable ais facility"). We originally wanted >> to enable it again for newer machine types, but apparently we forgot to do >> this so far. Let's do it for the new s390-ccw-virtio-5.0 machine now. >> >> While at it, also add a more verbose comment why we need the *_allowed() >> wrappers in s390-virtio-ccw.c. >> >> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1756946 >> Reviewed-by: David Hildenbrand >> Signed-off-by: Thomas Huth >> --- >> v3: Moved "s390mc->kvm_ais_allowed = false" to the end of the function >> >> hw/s390x/s390-virtio-ccw.c | 20 +++++++++++++++++--- >> include/hw/s390x/s390-virtio-ccw.h | 3 +++ >> target/s390x/kvm.c | 9 ++++++--- >> 3 files changed, 26 insertions(+), 6 deletions(-) > >> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c >> index 15260aeb9a..cf4fb4f2d9 100644 >> --- a/target/s390x/kvm.c >> +++ b/target/s390x/kvm.c >> @@ -365,10 +365,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s) >> /* >> * The migration interface for ais was introduced with kernel 4.13 >> * but the capability itself had been active since 4.12. As migration >> - * support is considered necessary let's disable ais in the 2.10 >> - * machine. >> + * support is considered necessary, we only try to enable this for >> + * newer machine types if KVM_CAP_S390_AIS_MIGRATION is available. >> */ >> - /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */ >> + if (kvm_ais_allowed() && >> + kvm_check_extension(s, KVM_CAP_S390_AIS_MIGRATION)) { > > Hnm, we actually need a kernel irqchip with the kvm flic to get ais to > work; else we'll fail with > > qemu-system-s390x: Failed to inject airq with AIS supported > > in the kernel_irqchip=off case, as we won't have an I/O adapter > registered. > > Adding 'kvm_kernel_irqchip_required() &&' seems to do the trick; > comments? > In spirit, I agree with this idea. But, a quick test shows that putting this check here results in ais=off for the 'none' machine case (libvirt capabilities detection). I think we have to only look at kvm_kernel_irqchip_required() when working with a real machine. >> + kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); >> + } >> >> kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES); >> return 0; > >