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Thu, 15 May 2025 11:26:40 +0000 (GMT) Date: Thu, 15 May 2025 13:14:47 +0200 From: Claudio Imbrenda To: Christoph Schlameuss Cc: kvm@vger.kernel.org, Christian Borntraeger , Janosch Frank , David Hildenbrand , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , linux-s390@vger.kernel.org Subject: Re: [PATCH 1/3] KVM: s390: Set KVM_MAX_VCPUS to 256 Message-ID: <20250515131447.5d99ce69@p-imbrenda> In-Reply-To: <20250514-rm-bsca-v1-1-6c2b065a8680@linux.ibm.com> References: <20250514-rm-bsca-v1-0-6c2b065a8680@linux.ibm.com> <20250514-rm-bsca-v1-1-6c2b065a8680@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: qiBadI-QXyyzfmEQyMSZ2QedaS9h_qiy X-Authority-Analysis: v=2.4 cv=ecg9f6EH c=1 sm=1 tr=0 ts=6825cf75 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=kj9zAlcOel0A:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=aIpEvDJpU-EyJW3OM6wA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: qiBadI-QXyyzfmEQyMSZ2QedaS9h_qiy X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTE1MDEwOSBTYWx0ZWRfXwxjvEDAgfL9S QnZEETnTuP2R5vbnyE4Yf0vPhy++h1MTIsbNUWHGqvCv+DV93PhUr71jFa1zw6i+WO1g+lTRUvx Qv0WSMycUjoEeLOj3/UL27leNAj+HIwJiqgP9eQuUQsqv1hH4TOt6mOJcM+0QoBMCxz96fYr3OD 0bPA72Rkg1R9FUWZ0WyeGNdBLQn2SFeF13KeFYIPCU0UzAISmZz9oheEJ+NeU5IYy/k0A3oGWMM FQCeuzEp4W9cFNPv6drC2AV4mxkVkv3UOIltQMlmGTXqqaweoCFZNOVmpVYkL65TUg2Mn4Wf15i Ops46q+ZIT5QwnQrjQ9eERQfUrsGjye1yi6iUtxOJ2WLsrxHO7KoDyc9xpQZtRWi84gAQblcxBa 4k4h9spDH85ALrUuRdRDtUtuCi7/sXSZ1aoOf6Q0wYmMmTjpsydnAUx++MTCmFSfQfcVkfMi X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-15_05,2025-05-14_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=881 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 bulkscore=0 suspectscore=0 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505070000 definitions=main-2505150109 On Wed, 14 May 2025 18:34:49 +0200 Christoph Schlameuss wrote: > The s390x architecture allows for 256 vCPUs with a max CPUID of 255. > The current KVM implementation limits this to 248 when using the > extended system control area (ESCA). So this correction should not cause > any real world problems but actually correct the values returned by the > ioctls: > > * KVM_CAP_NR_VCPUS > * KVM_CAP_MAX_VCPUS > * KVM_CAP_MAX_VCPU_ID > > KVM_MAX_VCPUS is also moved to kvm_host_types to allow using this in > future type definitions. > > Signed-off-by: Christoph Schlameuss Reviewed-by: Claudio Imbrenda > --- > arch/s390/include/asm/kvm_host.h | 2 -- > arch/s390/include/asm/kvm_host_types.h | 2 ++ > arch/s390/kvm/kvm-s390.c | 2 ++ > 3 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index cb89e54ada257eb4fdfe840ff37b2ea639c2d1cb..f51bac835260f562eaf4bbfd373a24bfdbc43834 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -27,8 +27,6 @@ > #include > #include > > -#define KVM_MAX_VCPUS 255 > - > #define KVM_INTERNAL_MEM_SLOTS 1 > > /* > diff --git a/arch/s390/include/asm/kvm_host_types.h b/arch/s390/include/asm/kvm_host_types.h > index 1394d3fb648f1e46dba2c513ed26e5dfd275fad4..9697db9576f6c39a6689251f85b4b974c344769a 100644 > --- a/arch/s390/include/asm/kvm_host_types.h > +++ b/arch/s390/include/asm/kvm_host_types.h > @@ -6,6 +6,8 @@ > #include > #include > > +#define KVM_MAX_VCPUS 256 > + > #define KVM_S390_BSCA_CPU_SLOTS 64 > #define KVM_S390_ESCA_CPU_SLOTS 248 > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 3f3175193fd7a7a26658eb2e2533d8037447a0b4..b65e4cbe67cf70a7d614607ebdd679060e7d31f4 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -638,6 +638,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > r = KVM_S390_ESCA_CPU_SLOTS; > if (ext == KVM_CAP_NR_VCPUS) > r = min_t(unsigned int, num_online_cpus(), r); > + else if (ext == KVM_CAP_MAX_VCPU_ID) > + r -= 1; > break; > case KVM_CAP_S390_COW: > r = machine_has_esop(); >