On 12/7/18 7:08 AM, Cornelia Huck wrote: > 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? >
Good call. I'll run some tests on this and see what happens. I'll report here on those results. >> >> typedef struct PSW { >> uint64_t mask; > -- Respectfully, - Collin Walling