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Commit 6a2fbec7 authored May 23, 2019 by Thomas Huth Committed by Greg Kroah-Hartman Jun 09, 2019

KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID



commit a86cb413f4bf273a9d341a3ab2c2ca44e12eb317 upstream.

KVM_CAP_MAX_VCPU_ID is currently always reporting KVM_MAX_VCPU_ID on all
architectures. However, on s390x, the amount of usable CPUs is determined
during runtime - it is depending on the features of the machine the code
is running on. Since we are using the vcpu_id as an index into the SCA
structures that are defined by the hardware (see e.g. the sca_add_vcpu()
function), it is not only the amount of CPUs that is limited by the hard-
ware, but also the range of IDs that we can use.
Thus KVM_CAP_MAX_VCPU_ID must be determined during runtime on s390x, too.
So the handling of KVM_CAP_MAX_VCPU_ID has to be moved from the common
code into the architecture specific code, and on s390x we have to return
the same value here as for KVM_CAP_MAX_VCPUS.
This problem has been discovered with the kvm_create_max_vcpus selftest.
With this change applied, the selftest now passes on s390x, too.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20190523164309.13345-9-thuth@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 3834630e

arch/mips/kvm/mips.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1099,6 +1099,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		case KVM_CAP_MAX_VCPUS:
		r = KVM_MAX_VCPUS;
		break;
		case KVM_CAP_MAX_VCPU_ID:
		r = KVM_MAX_VCPU_ID;
		break;
		case KVM_CAP_MIPS_FPU:
		/* We don't handle systems with inconsistent cpu_has_fpu */
		r = !!raw_cpu_has_fpu;

arch/powerpc/kvm/powerpc.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -632,6 +632,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		case KVM_CAP_MAX_VCPUS:
		r = KVM_MAX_VCPUS;
		break;
		case KVM_CAP_MAX_VCPU_ID:
		r = KVM_MAX_VCPU_ID;
		break;
		#ifdef CONFIG_PPC_BOOK3S_64
		case KVM_CAP_PPC_GET_SMMU_INFO:
		r = 1;

arch/s390/kvm/kvm-s390.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -489,6 +489,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		break;
		case KVM_CAP_NR_VCPUS:
		case KVM_CAP_MAX_VCPUS:
		case KVM_CAP_MAX_VCPU_ID:
		r = KVM_S390_BSCA_CPU_SLOTS;
		if (!kvm_s390_use_sca_entries())
		r = KVM_MAX_VCPUS;

arch/x86/kvm/x86.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2987,6 +2987,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		case KVM_CAP_MAX_VCPUS:
		r = KVM_MAX_VCPUS;
		break;
		case KVM_CAP_MAX_VCPU_ID:
		r = KVM_MAX_VCPU_ID;
		break;
		case KVM_CAP_NR_MEMSLOTS:
		r = KVM_USER_MEM_SLOTS;
		break;

virt/kvm/arm/arm.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -223,6 +223,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
		case KVM_CAP_MAX_VCPUS:
		r = KVM_MAX_VCPUS;
		break;
		case KVM_CAP_MAX_VCPU_ID:
		r = KVM_MAX_VCPU_ID;
		break;
		case KVM_CAP_NR_MEMSLOTS:
		r = KVM_USER_MEM_SLOTS;
		break;