From: Zeng Guang <guang.zeng@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Kim Phillips <kim.phillips@amd.com>,
Jarkko Sakkinen <jarkko@kernel.org>,
Jethro Beekman <jethro@fortanix.com>,
Kai Huang <kai.huang@intel.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Robert Hu <robert.hu@intel.com>, Gao Chao <chao.gao@intel.com>,
Zeng Guang <guang.zeng@intel.com>
Subject: [PATCH v8 8/9] KVM: x86: Allow userspace set maximum VCPU id for VM
Date: Mon, 11 Apr 2022 17:04:46 +0800 [thread overview]
Message-ID: <20220411090447.5928-9-guang.zeng@intel.com> (raw)
In-Reply-To: <20220411090447.5928-1-guang.zeng@intel.com>
Introduce new max_vcpu_ids in KVM for x86 architecture. Userspace
can assign maximum possible vcpu id for current VM session using
KVM_CAP_MAX_VCPU_ID of KVM_ENABLE_CAP ioctl().
This is done for x86 only because the sole use case is to guide
memory allocation for PID-pointer table, a structure needed to
enable VMX IPI.
By default, max_vcpu_ids set as KVM_MAX_VCPU_IDS.
Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Zeng Guang <guang.zeng@intel.com>
---
Documentation/virt/kvm/api.rst | 17 +++++++++++++++++
arch/x86/include/asm/kvm_host.h | 6 ++++++
arch/x86/kvm/x86.c | 18 +++++++++++++++++-
3 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index d13fa6600467..bb0b0f3edefe 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7136,6 +7136,23 @@ The valid bits in cap.args[0] are:
IA32_MISC_ENABLE[bit 18] is cleared.
=================================== ============================================
+7.32 KVM_CAP_MAX_VCPU_ID
+------------------------
+
+:Architectures: x86
+:Target: VM
+:Parameters: args[0] - maximum APIC ID value set for current VM
+:Returns: 0 on success, -EINVAL if args[0] is beyond KVM_MAX_VCPU_IDS
+ supported in KVM or if vCPU has been created.
+
+Userspace is able to calculate the limit to APIC ID values from designated CPU
+topology. This capability allows userspace to specify maximum possible APIC ID
+assigned for current VM session prior to the creation of vCPUs. KVM can manage
+memory allocation of VM-scope structures which depends on the value of APIC ID.
+
+Calling KVM_CHECK_EXTENSION for this capability returns the value of maximum APIC
+ID that KVM supports at runtime. It sets as KVM_MAX_VCPU_IDS in VM initialization.
+
8. Other capabilities.
======================
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d23e80a56eb8..cdd14033988d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1238,6 +1238,12 @@ struct kvm_arch {
hpa_t hv_root_tdp;
spinlock_t hv_root_tdp_lock;
#endif
+ /*
+ * VM-scope maximum vCPU ID. Used to determine the size of structures
+ * that increase along with the maximum vCPU ID, in which case, using
+ * the global KVM_MAX_VCPU_IDS may lead to significant memory waste.
+ */
+ u32 max_vcpu_ids;
};
struct kvm_vm_stat {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0c0ca599a353..d1a39285deab 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4320,7 +4320,7 @@ 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_IDS;
+ r = kvm->arch.max_vcpu_ids;
break;
case KVM_CAP_PV_MMU: /* obsolete */
r = 0;
@@ -6064,6 +6064,18 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
}
mutex_unlock(&kvm->lock);
break;
+ case KVM_CAP_MAX_VCPU_ID:
+ r = -EINVAL;
+ if (cap->args[0] > KVM_MAX_VCPU_IDS)
+ break;
+
+ mutex_lock(&kvm->lock);
+ if (!kvm->created_vcpus) {
+ kvm->arch.max_vcpu_ids = cap->args[0];
+ r = 0;
+ }
+ mutex_unlock(&kvm->lock);
+ break;
default:
r = -EINVAL;
break;
@@ -11180,6 +11192,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
struct page *page;
int r;
+ if (vcpu->vcpu_id >= vcpu->kvm->arch.max_vcpu_ids)
+ return -EINVAL;
+
vcpu->arch.last_vmentry_cpu = -1;
vcpu->arch.regs_avail = ~0;
vcpu->arch.regs_dirty = ~0;
@@ -11704,6 +11719,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
spin_lock_init(&kvm->arch.hv_root_tdp_lock);
kvm->arch.hv_root_tdp = INVALID_PAGE;
#endif
+ kvm->arch.max_vcpu_ids = KVM_MAX_VCPU_IDS;
INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
--
2.27.0
next prev parent reply other threads:[~2022-04-11 9:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-11 9:04 [PATCH v8 0/9] IPI virtualization support for VM Zeng Guang
2022-04-11 9:04 ` [PATCH v8 1/9] x86/cpu: Add new VMX feature, Tertiary VM-Execution control Zeng Guang
2022-04-11 9:04 ` [PATCH v8 2/9] KVM: VMX: Extend BUILD_CONTROLS_SHADOW macro to support 64-bit variation Zeng Guang
2022-04-11 9:04 ` [PATCH v8 3/9] KVM: VMX: Detect Tertiary VM-Execution control when setup VMCS config Zeng Guang
2022-04-11 9:04 ` [PATCH v8 4/9] KVM: VMX: Report tertiary_exec_control field in dump_vmcs() Zeng Guang
2022-04-11 9:04 ` [PATCH v8 5/9] KVM: x86: Add support for vICR APIC-write VM-Exits in x2APIC mode Zeng Guang
2022-04-11 9:04 ` [PATCH v8 6/9] KVM: x86: lapic: don't allow to change APIC ID unconditionally Zeng Guang
2022-04-15 14:39 ` Sean Christopherson
2022-04-19 14:07 ` Maxim Levitsky
2022-04-26 8:14 ` Maxim Levitsky
2022-04-26 14:00 ` Chao Gao
2022-04-11 9:04 ` [PATCH v8 7/9] KVM: Move kvm_arch_vcpu_precreate() under kvm->lock Zeng Guang
2022-04-15 15:00 ` Sean Christopherson
2022-04-15 15:11 ` Sean Christopherson
2022-04-11 9:04 ` Zeng Guang [this message]
2022-04-15 15:01 ` [PATCH v8 8/9] KVM: x86: Allow userspace set maximum VCPU id for VM Sean Christopherson
2022-04-11 9:04 ` [PATCH v8 9/9] KVM: VMX: enable IPI virtualization Zeng Guang
2022-04-15 15:25 ` Sean Christopherson
2022-04-18 9:25 ` Chao Gao
2022-04-18 15:14 ` Sean Christopherson
2022-04-19 0:00 ` Chao Gao
2022-04-18 12:49 ` Zeng Guang
2022-04-15 15:45 ` Sean Christopherson
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