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Mon, 12 Apr 2021 22:27:04 +0000 (GMT) Received: from farosas.linux.ibm.com.com (unknown [9.211.82.34]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 12 Apr 2021 22:27:04 +0000 (GMT) From: Fabiano Rosas To: kvm-ppc@vger.kernel.org Subject: [RFC PATCH 2/2] KVM: PPC: Book3S HV: Provide a more accurate MAX_VCPU_ID in P9 Date: Mon, 12 Apr 2021 19:26:56 -0300 Message-Id: <20210412222656.3466987-3-farosas@linux.ibm.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210412222656.3466987-1-farosas@linux.ibm.com> References: <20210412222656.3466987-1-farosas@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: oCn6YlPUZtVWsAbTJdrY0kke-9Qv5__6 X-Proofpoint-ORIG-GUID: oCn6YlPUZtVWsAbTJdrY0kke-9Qv5__6 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-04-12_11:2021-04-12, 2021-04-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 phishscore=0 mlxlogscore=967 impostorscore=0 adultscore=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 spamscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104120142 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, groug@kaod.org, david@gibson.dropbear.id.au Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" The KVM_CAP_MAX_VCPU_ID capability was added by commit 0b1b1dfd52a6 ("kvm: introduce KVM_MAX_VCPU_ID") to allow for vcpu ids larger than KVM_MAX_VCPU in powerpc. For a P9 host we depend on the guest VSMT value to know what is the maximum number of vcpu id we can support: kvmppc_core_vcpu_create_hv: (...) if (cpu_has_feature(CPU_FTR_ARCH_300)) { --> if (id >= (KVM_MAX_VCPUS * kvm->arch.emul_smt_mode)) { pr_devel("KVM: VCPU ID too high\n"); core = KVM_MAX_VCORES; } else { BUG_ON(kvm->arch.smt_mode != 1); core = kvmppc_pack_vcpu_id(kvm, id); } } else { core = id / kvm->arch.smt_mode; } which means that the value being returned by the capability today for a given guest is potentially way larger than what we actually support: \#define KVM_MAX_VCPU_ID (MAX_SMT_THREADS * KVM_MAX_VCORES) If the capability is queried before userspace enables the KVM_CAP_PPC_SMT ioctl there is not much we can do, but if the emulated smt mode is already known we could provide a more accurate value. The only practical effect of this change today is to make the kvm_create_max_vcpus test pass for powerpc. The QEMU spapr machine has a lower max vcpu than what KVM allows so even KVM_MAX_VCPU is not reached. Signed-off-by: Fabiano Rosas --- I see that for ppc, QEMU uses the capability after enabling KVM_CAP_PPC_SMT, so we could change QEMU to issue the check extension on the vm fd so that it would get the more accurate value. --- arch/powerpc/kvm/powerpc.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index a2a68a958fa0..95c9f47cc1b3 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -649,7 +649,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_MAX_VCPUS; break; case KVM_CAP_MAX_VCPU_ID: - r = KVM_MAX_VCPU_ID; + if (hv_enabled && cpu_has_feature(CPU_FTR_ARCH_300)) + r = KVM_MAX_VCPUS * ((kvm) ? kvm->arch.emul_smt_mode : 1); + else + r = KVM_MAX_VCPU_ID; break; #ifdef CONFIG_PPC_BOOK3S_64 case KVM_CAP_PPC_GET_SMMU_INFO: