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Thu, 12 May 2022 09:52:52 +0000 (GMT) Received: from p-imbrenda (unknown [9.145.10.145]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 12 May 2022 09:52:52 +0000 (GMT) Date: Thu, 12 May 2022 11:52:50 +0200 From: Claudio Imbrenda To: David Hildenbrand Cc: Pierre Morel , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, cohuck@redhat.com, thuth@redhat.com, hca@linux.ibm.com, gor@linux.ibm.com, wintera@linux.ibm.com, seiden@linux.ibm.com, nrb@linux.ibm.com Subject: Re: [PATCH v9 3/3] s390x: KVM: resetting the Topology-Change-Report Message-ID: <20220512115250.2e20bfdf@p-imbrenda> In-Reply-To: <76fd0c11-5b9b-0032-183b-54db650f13b1@redhat.com> References: <20220506092403.47406-1-pmorel@linux.ibm.com> <20220506092403.47406-4-pmorel@linux.ibm.com> <76fd0c11-5b9b-0032-183b-54db650f13b1@redhat.com> Organization: IBM X-Mailer: Claws Mail 4.1.0 (GTK 3.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: bd2hnMZHZ75ZzlKZPdY27co-4clii1x3 X-Proofpoint-ORIG-GUID: YSsDv-q-V0U9jIh7WTqn0g6e_xDG3SmX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-12_02,2022-05-12_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 spamscore=0 priorityscore=1501 bulkscore=0 adultscore=0 suspectscore=0 lowpriorityscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205120044 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 12 May 2022 11:31:18 +0200 David Hildenbrand wrote: > On 06.05.22 11:24, Pierre Morel wrote: > > During a subsystem reset the Topology-Change-Report is cleared. > > Let's give userland the possibility to clear the MTCR in the case > > of a subsystem reset. > > > > To migrate the MTCR, let's give userland the possibility to > > query the MTCR state. > > > > Signed-off-by: Pierre Morel > > --- > > arch/s390/include/uapi/asm/kvm.h | 5 ++ > > arch/s390/kvm/kvm-s390.c | 79 ++++++++++++++++++++++++++++++++ > > 2 files changed, 84 insertions(+) > > > > diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h > > index 7a6b14874d65..abdcf4069343 100644 > > --- a/arch/s390/include/uapi/asm/kvm.h > > +++ b/arch/s390/include/uapi/asm/kvm.h > > @@ -74,6 +74,7 @@ struct kvm_s390_io_adapter_req { > > #define KVM_S390_VM_CRYPTO 2 > > #define KVM_S390_VM_CPU_MODEL 3 > > #define KVM_S390_VM_MIGRATION 4 > > +#define KVM_S390_VM_CPU_TOPOLOGY 5 > > > > /* kvm attributes for mem_ctrl */ > > #define KVM_S390_VM_MEM_ENABLE_CMMA 0 > > @@ -171,6 +172,10 @@ struct kvm_s390_vm_cpu_subfunc { > > #define KVM_S390_VM_MIGRATION_START 1 > > #define KVM_S390_VM_MIGRATION_STATUS 2 > > > > +/* kvm attributes for cpu topology */ > > +#define KVM_S390_VM_CPU_TOPO_MTR_CLEAR 0 > > +#define KVM_S390_VM_CPU_TOPO_MTR_SET 1 > > + > > /* for KVM_GET_REGS and KVM_SET_REGS */ > > struct kvm_regs { > > /* general purpose regs for s390 */ > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > > index c8bdce31464f..80a1244f0ead 100644 > > --- a/arch/s390/kvm/kvm-s390.c > > +++ b/arch/s390/kvm/kvm-s390.c > > @@ -1731,6 +1731,76 @@ static void kvm_s390_sca_set_mtcr(struct kvm *kvm) > > ipte_unlock(kvm); > > } > > > > +/** > > + * kvm_s390_sca_clear_mtcr > > + * @kvm: guest KVM description > > + * > > + * Is only relevant if the topology facility is present, > > + * the caller should check KVM facility 11 > > + * > > + * Updates the Multiprocessor Topology-Change-Report to signal > > + * the guest with a topology change. > > + */ > > +static void kvm_s390_sca_clear_mtcr(struct kvm *kvm) > > +{ > > + struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */ > > + > > + ipte_lock(kvm); > > + sca->utility &= ~SCA_UTILITY_MTCR; > > > One space too much. > > sca->utility &= ~SCA_UTILITY_MTCR; > > > + ipte_unlock(kvm); > > +} > > + > > +static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr) > > +{ > > + if (!test_kvm_facility(kvm, 11)) > > + return -ENXIO; > > + > > + switch (attr->attr) { > > + case KVM_S390_VM_CPU_TOPO_MTR_SET: > > + kvm_s390_sca_set_mtcr(kvm); > > + break; > > + case KVM_S390_VM_CPU_TOPO_MTR_CLEAR: > > + kvm_s390_sca_clear_mtcr(kvm); > > + break; > > + } > > + return 0; > > +} > > + > > +/** > > + * kvm_s390_sca_get_mtcr > > + * @kvm: guest KVM description > > + * > > + * Is only relevant if the topology facility is present, > > + * the caller should check KVM facility 11 > > + * > > + * reports to QEMU the Multiprocessor Topology-Change-Report. > > + */ > > +static int kvm_s390_sca_get_mtcr(struct kvm *kvm) > > +{ > > + struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */ > > + int val; > > + > > + ipte_lock(kvm); > > + val = !!(sca->utility & SCA_UTILITY_MTCR); > > + ipte_unlock(kvm); > > + > > + return val; > > +} > > + > > +static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr) > > +{ > > + int mtcr; > > I think we prefer something like u16 when copying to user space. but then userspace also has to expect a u16, right? > > > + > > + if (!test_kvm_facility(kvm, 11)) > > + return -ENXIO; > > + > > + mtcr = kvm_s390_sca_get_mtcr(kvm); > > + if (copy_to_user((void __user *)attr->addr, &mtcr, sizeof(mtcr))) > > + return -EFAULT; > > + > > + return 0; > > +} > > You should probably add documentation, and document that only the last > bit (0x1) has a meaning. > > Apart from that LGTM. >