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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andrew Jones <drjones@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Thomas Huth <thuth@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>
Subject: [PATCH 4.14 46/69] KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID
Date:   Fri,  7 Jun 2019 17:39:27 +0200
Message-Id: <20190607153854.077761066@linuxfoundation.org>
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From: Thomas Huth <thuth@redhat.com>

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>


---
 arch/mips/kvm/mips.c       |    3 +++
 arch/powerpc/kvm/powerpc.c |    3 +++
 arch/s390/kvm/kvm-s390.c   |    1 +
 arch/x86/kvm/x86.c         |    3 +++
 virt/kvm/arm/arm.c         |    3 +++
 virt/kvm/kvm_main.c        |    2 --
 6 files changed, 13 insertions(+), 2 deletions(-)

--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1078,6 +1078,9 @@ int kvm_vm_ioctl_check_extension(struct
 	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;
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -629,6 +629,9 @@ int kvm_vm_ioctl_check_extension(struct
 	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;
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -428,6 +428,7 @@ int kvm_vm_ioctl_check_extension(struct
 		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;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2825,6 +2825,9 @@ int kvm_vm_ioctl_check_extension(struct
 	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;
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -217,6 +217,9 @@ int kvm_vm_ioctl_check_extension(struct
 	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;
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2964,8 +2964,6 @@ static long kvm_vm_ioctl_check_extension
 	case KVM_CAP_MULTI_ADDRESS_SPACE:
 		return KVM_ADDRESS_SPACE_NUM;
 #endif
-	case KVM_CAP_MAX_VCPU_ID:
-		return KVM_MAX_VCPU_ID;
 	default:
 		break;
 	}