On Wed, Jun 26, 2019 at 11:49:03AM +0200, Richard Henderson wrote: > On 6/21/19 6:34 PM, Andrew Jones wrote: > > We first convert the pmu property from a static property to one with > > its own accessors. Then we use the set accessor to check if the PMU is > > supported when using KVM. Indeed a 32-bit KVM host does not support > > the PMU, so this check will catch an attempt to use it at property-set > > time. > > > > Signed-off-by: Andrew Jones <drjo...@redhat.com> > > --- > > target/arm/cpu.c | 30 +++++++++++++++++++++++++----- > > target/arm/kvm.c | 9 +++++++++ > > target/arm/kvm_arm.h | 13 +++++++++++++ > > 3 files changed, 47 insertions(+), 5 deletions(-) > > > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > > index 376db154f008..858f668d226e 100644 > > --- a/target/arm/cpu.c > > +++ b/target/arm/cpu.c > > @@ -759,10 +759,6 @@ static Property arm_cpu_has_el3_property = > > static Property arm_cpu_cfgend_property = > > DEFINE_PROP_BOOL("cfgend", ARMCPU, cfgend, false); > > > > -/* use property name "pmu" to match other archs and virt tools */ > > -static Property arm_cpu_has_pmu_property = > > - DEFINE_PROP_BOOL("pmu", ARMCPU, has_pmu, true); > > - > > static Property arm_cpu_has_vfp_property = > > DEFINE_PROP_BOOL("vfp", ARMCPU, has_vfp, true); > > > > @@ -785,6 +781,29 @@ static Property arm_cpu_pmsav7_dregion_property = > > pmsav7_dregion, > > qdev_prop_uint32, uint32_t); > > > > +static bool arm_get_pmu(Object *obj, Error **errp) > > +{ > > + ARMCPU *cpu = ARM_CPU(obj); > > + > > + return cpu->has_pmu; > > +} > > + > > +static void arm_set_pmu(Object *obj, bool value, Error **errp) > > +{ > > + ARMCPU *cpu = ARM_CPU(obj); > > + > > + if (value) { > > + if (kvm_enabled() && !kvm_arm_pmu_supported(CPU(cpu))) { > > + error_setg(errp, "'pmu' feature not supported by KVM on this > > host"); > > + return; > > + } > > + set_feature(&cpu->env, ARM_FEATURE_PMU); > > + } else { > > + unset_feature(&cpu->env, ARM_FEATURE_PMU); > > + } > > + cpu->has_pmu = value; > > +} > > + > > static void arm_get_init_svtor(Object *obj, Visitor *v, const char *name, > > void *opaque, Error **errp) > > { > > @@ -859,7 +878,8 @@ void arm_cpu_post_init(Object *obj) > > } > > > > if (arm_feature(&cpu->env, ARM_FEATURE_PMU)) { > > - qdev_property_add_static(DEVICE(obj), &arm_cpu_has_pmu_property, > > + cpu->has_pmu = true; > > + object_property_add_bool(obj, "pmu", arm_get_pmu, arm_set_pmu, > > &error_abort); > > This doesn't look right. > > The static property is only enabled here if the cpu is known to support the > PMU, and thus the only useful setting is -cpu foo,pmu=off. Which means that > the extra checking that you do in the dynamic property is unused.
It's used when attempting to do '-cpu foo,pmu=on' on a cpu model that would support the PMU on TCG, and thus has the property, but won't work when KVM is in use. I'll admit I didn't test this, because I don't have 32-bit KVM hosts available, but I'm pretty sure it should work as expected: -accel tcg -cpu foo <-- on by default -accel tcg -cpu foo,pmu=off <-- off -accel tcg -cpu foo,pmu=on <-- nop -accel kvm -cpu foo <-- on by default if kvm+foo supports the pmu, otherwise off -accel kvm -cpu foo,pmu=off <-- off -accel kvm -cpu foo,pmu=on <-- nop if kvm+foo supports the pmu, otherwise error message With the error message, which will only occur with 32-bit kvm hosts, since 64-bit kvm hosts have all supported the pmu for quite some time, being the only new thing. > > It seems like you need to be checking for the PMU earlier, e.g. in > kvm_arm_get_host_cpu_features. We need to push all the checks into property accessors if we want the QMP command to work for them. Thanks, drew