On Thu, 6 Dec 2018 17:24:17 -0500 Collin Walling <wall...@linux.ibm.com> wrote:
> Diagnose 318 is a new z14.2 CPU feature. Since we are able to emulate > it entirely via KVM, we can add guest support for earlier models. A > new CPU feature for diagnose 318 (shortened to diag318) will be made > available to guests starting with the zEC12-full CPU model. > > The z14.2 adds a new read SCP info byte (let's call it byte 134) to > detect the availability of diag318. Because of this, we have room for > one less VCPU and thus limit the max VPUs supported in a configuration > to 247 (down from 248). > > Signed-off-by: Collin Walling <wall...@linux.ibm.com>. > --- > hw/s390x/sclp.c | 2 ++ > include/hw/s390x/sclp.h | 2 ++ > target/s390x/cpu.h | 2 +- > target/s390x/cpu_features.c | 3 +++ > target/s390x/cpu_features.h | 1 + > target/s390x/cpu_features_def.h | 3 +++ > target/s390x/gen-features.c | 1 + > target/s390x/kvm.c | 1 + > 8 files changed, 14 insertions(+), 1 deletion(-) > > diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h > index 8c2320e..594b4a4 100644 > --- a/target/s390x/cpu.h > +++ b/target/s390x/cpu.h > @@ -52,7 +52,7 @@ > > #define MMU_USER_IDX 0 > > -#define S390_MAX_CPUS 248 > +#define S390_MAX_CPUS 247 Isn't that already problematic if you try to migrate from an older QEMU with all possible vcpus defined? IOW, don't you really need a way that older machines can still run with one more vcpu? > > typedef struct PSW { > uint64_t mask;