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Thu, 14 May 2020 18:53:29 +0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 04EIrPNU9961918 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 May 2020 18:53:25 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DD769C6055; Thu, 14 May 2020 18:53:25 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3278CC6057; Thu, 14 May 2020 18:53:25 +0000 (GMT) Received: from localhost.localdomain (unknown [9.85.130.116]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTPS; Thu, 14 May 2020 18:53:25 +0000 (GMT) Subject: Re: [PATCH v6 2/2] s390/kvm: diagnose 318 handling To: Thomas Huth , David Hildenbrand , Janosch Frank , kvm@vger.kernel.org, linux-s390@vger.kernel.org Cc: pbonzini@redhat.com, borntraeger@de.ibm.com, cohuck@redhat.com, imbrenda@linux.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com References: <20200513221557.14366-1-walling@linux.ibm.com> <20200513221557.14366-3-walling@linux.ibm.com> <88d27a61-b55b-ee68-f7f9-85ce7fcefd64@redhat.com> <516405b3-67c4-aa12-1fa5-772e401e4403@redhat.com> <2aa0d573-b9d4-8022-9ec5-79f7156d1bcb@linux.ibm.com> From: Collin Walling Message-ID: Date: Thu, 14 May 2020 14:53:24 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: 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=2.50.10434:6.0.216,18.0.676 definitions=2020-05-14_06:2020-05-14,2020-05-14 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 spamscore=0 priorityscore=1501 impostorscore=0 cotscore=-2147483648 clxscore=1015 mlxscore=0 malwarescore=0 mlxlogscore=999 phishscore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005140160 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 5/14/20 2:37 PM, Thomas Huth wrote: > On 14/05/2020 19.20, Collin Walling wrote: >> On 5/14/20 5:53 AM, David Hildenbrand wrote: >>> On 14.05.20 11:49, Janosch Frank wrote: >>>> On 5/14/20 11:37 AM, David Hildenbrand wrote: >>>>> On 14.05.20 10:52, Janosch Frank wrote: >>>>>> On 5/14/20 9:53 AM, Thomas Huth wrote: >>>>>>> On 14/05/2020 00.15, Collin Walling wrote: >>>>>>>> DIAGNOSE 0x318 (diag318) is a privileged s390x instruction that must >>>>>>>> be intercepted by SIE and handled via KVM. Let's introduce some >>>>>>>> functions to communicate between userspace and KVM via ioctls. These >>>>>>>> will be used to get/set the diag318 related information, as well as >>>>>>>> check the system if KVM supports handling this instruction. >>>>>>>> >>>>>>>> This information can help with diagnosing the environment the VM is >>>>>>>> running in (Linux, z/VM, etc) if the OS calls this instruction. >>>>>>>> >>>>>>>> By default, this feature is disabled and can only be enabled if a >>>>>>>> user space program (such as QEMU) explicitly requests it. >>>>>>>> >>>>>>>> The Control Program Name Code (CPNC) is stored in the SIE block >>>>>>>> and a copy is retained in each VCPU. The Control Program Version >>>>>>>> Code (CPVC) is not designed to be stored in the SIE block, so we >>>>>>>> retain a copy in each VCPU next to the CPNC. >>>>>>>> >>>>>>>> Signed-off-by: Collin Walling >>>>>>>> --- >>>>>>>> Documentation/virt/kvm/devices/vm.rst | 29 +++++++++ >>>>>>>> arch/s390/include/asm/kvm_host.h | 6 +- >>>>>>>> arch/s390/include/uapi/asm/kvm.h | 5 ++ >>>>>>>> arch/s390/kvm/diag.c | 20 ++++++ >>>>>>>> arch/s390/kvm/kvm-s390.c | 89 +++++++++++++++++++++++++++ >>>>>>>> arch/s390/kvm/kvm-s390.h | 1 + >>>>>>>> arch/s390/kvm/vsie.c | 2 + >>>>>>>> 7 files changed, 151 insertions(+), 1 deletion(-) >>>>>>> [...] >>>>>>>> diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c >>>>>>>> index 563429dece03..3caed4b880c8 100644 >>>>>>>> --- a/arch/s390/kvm/diag.c >>>>>>>> +++ b/arch/s390/kvm/diag.c >>>>>>>> @@ -253,6 +253,24 @@ static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu) >>>>>>>> return ret < 0 ? ret : 0; >>>>>>>> } >>>>>>>> >>>>>>>> +static int __diag_set_diag318_info(struct kvm_vcpu *vcpu) >>>>>>>> +{ >>>>>>>> + unsigned int reg = (vcpu->arch.sie_block->ipa & 0xf0) >> 4; >>>>>>>> + u64 info = vcpu->run->s.regs.gprs[reg]; >>>>>>>> + >>>>>>>> + if (!vcpu->kvm->arch.use_diag318) >>>>>>>> + return -EOPNOTSUPP; >>>>>>>> + >>>>>>>> + vcpu->stat.diagnose_318++; >>>>>>>> + kvm_s390_set_diag318_info(vcpu->kvm, info); >>>>>>>> + >>>>>>>> + VCPU_EVENT(vcpu, 3, "diag 0x318 cpnc: 0x%x cpvc: 0x%llx", >>>>>>>> + vcpu->kvm->arch.diag318_info.cpnc, >>>>>>>> + (u64)vcpu->kvm->arch.diag318_info.cpvc); >> >> Errr.. thought I dropped this message. We favored just using the >> VM_EVENT from last time. >> >>>>>>>> + >>>>>>>> + return 0; >>>>>>>> +} >>>>>>>> + >>>>>>>> int kvm_s390_handle_diag(struct kvm_vcpu *vcpu) >>>>>>>> { >>>>>>>> int code = kvm_s390_get_base_disp_rs(vcpu, NULL) & 0xffff; >>>>>>>> @@ -272,6 +290,8 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu) >>>>>>>> return __diag_page_ref_service(vcpu); >>>>>>>> case 0x308: >>>>>>>> return __diag_ipl_functions(vcpu); >>>>>>>> + case 0x318: >>>>>>>> + return __diag_set_diag318_info(vcpu); >>>>>>>> case 0x500: >>>>>>>> return __diag_virtio_hypercall(vcpu); >>>>>>> >>>>>>> I wonder whether it would make more sense to simply drop to userspace >>>>>>> and handle the diag 318 call there? That way the userspace would always >>>>>>> be up-to-date, and as we've seen in the past (e.g. with the various SIGP >>>>>>> handling), it's better if the userspace is in control... e.g. userspace >>>>>>> could also decide to only use KVM_S390_VM_MISC_ENABLE_DIAG318 if the >>>>>>> guest just executed the diag 318 instruction. >>>>>>> >>>>>>> And you need the kvm_s390_vm_get/set_misc functions anyway, so these >>>>>>> could also be simply used by the diag 318 handler in userspace? >> >> Pardon my ignorance, but I do not think I fully understand what exactly >> should be dropped in favor of doing things in userspace. >> >> My assumption: if a diag handler is not found in KVM, then we >> fallthrough to userspace handling? > > Right, if you simply omit this change to diag.c, the default case > returns -EOPNOTSUPP which then should cause an exit to userspace. You > can then add the code in QEMU to handle_diag() in target/s390x/kvm.c > instead. > > Thomas > Very cool! Okay, I think this makes sense, then. I'll look into this. Thanks for the tip. @Conny, I assume this is what you meant as well? If so, ignore my response I sent earlier :) -- -- Regards, Collin Stay safe and stay healthy