KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID

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>

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 6d0517a..0369f26 100644 (file)
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1122,6 +1122,9 @@ 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;

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 3393b16..aa3a678 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -657,6 +657,9 @@ 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;

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e5e8eb2..28ebd64 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -539,6 +539,7 @@ 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;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index acb179f..83aefd7 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3122,6 +3122,9 @@ 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_PV_MMU:    /* obsolete */
                r = 0;
                break;

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 90cedeb..7eeebe5 100644 (file)
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -224,6 +224,9 @@ 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_MSI_DEVID:
                if (!kvm)
                        r = -EINVAL;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 301089a..ca54b09 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3151,8 +3151,6 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
        case KVM_CAP_MULTI_ADDRESS_SPACE:
                return KVM_ADDRESS_SPACE_NUM;
 #endif
-       case KVM_CAP_MAX_VCPU_ID:
-               return KVM_MAX_VCPU_ID;
        case KVM_CAP_NR_MEMSLOTS:
                return KVM_USER_MEM_SLOTS;
        default: