From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:23987 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726589AbgEOGRI (ORCPT ); Fri, 15 May 2020 02:17:08 -0400 Date: Fri, 15 May 2020 08:16:52 +0200 From: Cornelia Huck Subject: Re: [PATCH v6 2/2] s390/kvm: diagnose 318 handling Message-ID: <20200515081652.62c33498.cohuck@redhat.com> In-Reply-To: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Collin Walling Cc: Thomas Huth , David Hildenbrand , Janosch Frank , kvm@vger.kernel.org, linux-s390@vger.kernel.org, pbonzini@redhat.com, borntraeger@de.ibm.com, imbrenda@linux.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com On Thu, 14 May 2020 14:53:24 -0400 Collin Walling wrote: > 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 :) > Yes; if done correctly, it should be easy to hack something up for tcg as well, if we want it.