[PATCH v2 1/3] KVM: s390: Set KVM_MAX_VCPUS to 256

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

The s390x architecture allows for 256 vCPUs with a max CPUID of 255.
The current KVM implementation limits this to 248 when using the
extended system control area (ESCA). So this correction should not cause
any real world problems but actually correct the values returned by the
ioctls:

* KVM_CAP_NR_VCPUS
* KVM_CAP_MAX_VCPUS
* KVM_CAP_MAX_VCPU_ID

KVM_MAX_VCPUS is also moved to kvm_host_types to allow using this in
future type definitions.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h       | 2 --
 arch/s390/include/asm/kvm_host_types.h | 2 ++
 arch/s390/kvm/kvm-s390.c               | 2 ++
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index cb89e54ada257eb4fdfe840ff37b2ea639c2d1cb..f51bac835260f562eaf4bbfd373a24bfdbc43834 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -27,8 +27,6 @@
 #include <asm/isc.h>
 #include <asm/guarded_storage.h>
 
-#define KVM_MAX_VCPUS 255
-
 #define KVM_INTERNAL_MEM_SLOTS 1
 
 /*
diff --git a/arch/s390/include/asm/kvm_host_types.h b/arch/s390/include/asm/kvm_host_types.h
index 1394d3fb648f1e46dba2c513ed26e5dfd275fad4..9697db9576f6c39a6689251f85b4b974c344769a 100644
--- a/arch/s390/include/asm/kvm_host_types.h
+++ b/arch/s390/include/asm/kvm_host_types.h
@@ -6,6 +6,8 @@
 #include <linux/atomic.h>
 #include <linux/types.h>
 
+#define KVM_MAX_VCPUS 256
+
 #define KVM_S390_BSCA_CPU_SLOTS 64
 #define KVM_S390_ESCA_CPU_SLOTS 248
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3f3175193fd7a7a26658eb2e2533d8037447a0b4..b65e4cbe67cf70a7d614607ebdd679060e7d31f4 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -638,6 +638,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 			r = KVM_S390_ESCA_CPU_SLOTS;
 		if (ext == KVM_CAP_NR_VCPUS)
 			r = min_t(unsigned int, num_online_cpus(), r);
+		else if (ext == KVM_CAP_MAX_VCPU_ID)
+			r -= 1;
 		break;
 	case KVM_CAP_S390_COW:
 		r = machine_has_esop();

-- 
2.49.0