On Wed, 14 May 2025 18:34:49 +0200 Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx> wrote: > 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. > > Signed-off-by: Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx> Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> > --- > 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(); >
