On 1/29/2026 7:09 AM, Zide Chen wrote: > Since the lbr-fmt property is masked with PERF_CAP_LBR_FMT in > DEFINE_PROP_UINT64_CHECKMASK(), there is no need to explicitly validate > user-requested lbr-fmt values. > > The PMU feature is only supported when running under KVM, so initialize > cpu->lbr_fmt in kvm_cpu_instance_init(). Use -1 as the default lbr-fmt, > rather than initializing it with ~PERF_CAP_LBR_FMT, which is misleading > as it suggests a semantic relationship that does not exist. > > Rename requested_lbr_fmt to a more generic guest_fmt. When lbr-fmt is > not specified and cpu->migratable is false, the guest lbr_fmt value is > not user-requested. > > Signed-off-by: Zide Chen <[email protected]> > --- > V2: > - New patch. > > target/i386/cpu.c | 18 ++++++------------ > target/i386/kvm/kvm-cpu.c | 2 ++ > 2 files changed, 8 insertions(+), 12 deletions(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index f2c83b4f259c..09180c718d58 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -9788,7 +9788,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error > **errp) > X86CPUClass *xcc = X86_CPU_GET_CLASS(dev); > CPUX86State *env = &cpu->env; > Error *local_err = NULL; > - unsigned requested_lbr_fmt; > + unsigned guest_fmt; > > if (!kvm_enabled()) > cpu->enable_pmu = false; > @@ -9828,11 +9828,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error > **errp) > * Override env->features[FEAT_PERF_CAPABILITIES].LBR_FMT > * with user-provided setting. > */ > - if (cpu->lbr_fmt != ~PERF_CAP_LBR_FMT) { > - if ((cpu->lbr_fmt & PERF_CAP_LBR_FMT) != cpu->lbr_fmt) { > - error_setg(errp, "invalid lbr-fmt"); > - return; > - } > + if (cpu->lbr_fmt != -1) { > env->features[FEAT_PERF_CAPABILITIES] &= ~PERF_CAP_LBR_FMT; > env->features[FEAT_PERF_CAPABILITIES] |= cpu->lbr_fmt; > } > @@ -9841,9 +9837,8 @@ static void x86_cpu_realizefn(DeviceState *dev, Error > **errp) > * vPMU LBR is supported when 1) KVM is enabled 2) Option pmu=on and > * 3)vPMU LBR format matches that of host setting. > */ > - requested_lbr_fmt = > - env->features[FEAT_PERF_CAPABILITIES] & PERF_CAP_LBR_FMT; > - if (requested_lbr_fmt && kvm_enabled()) { > + guest_fmt = env->features[FEAT_PERF_CAPABILITIES] & PERF_CAP_LBR_FMT; > + if (guest_fmt) { > uint64_t host_perf_cap = > x86_cpu_get_supported_feature_word(NULL, FEAT_PERF_CAPABILITIES); > unsigned host_lbr_fmt = host_perf_cap & PERF_CAP_LBR_FMT; > @@ -9852,10 +9847,10 @@ static void x86_cpu_realizefn(DeviceState *dev, Error > **errp) > error_setg(errp, "vPMU: LBR is unsupported without pmu=on"); > return; > } > - if (requested_lbr_fmt != host_lbr_fmt) { > + if (guest_fmt != host_lbr_fmt) { > error_setg(errp, "vPMU: the lbr-fmt value (0x%x) does not match " > "the host value (0x%x).", > - requested_lbr_fmt, host_lbr_fmt); > + guest_fmt, host_lbr_fmt); > return; > } > } > @@ -10279,7 +10274,6 @@ static void x86_cpu_initfn(Object *obj) > object_property_add_alias(obj, "sse4_2", obj, "sse4.2"); > > object_property_add_alias(obj, "hv-apicv", obj, "hv-avic"); > - cpu->lbr_fmt = ~PERF_CAP_LBR_FMT; > object_property_add_alias(obj, "lbr_fmt", obj, "lbr-fmt"); > > if (xcc->model) { > diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c > index 33a8c26bc27c..b4500ab69f82 100644 > --- a/target/i386/kvm/kvm-cpu.c > +++ b/target/i386/kvm/kvm-cpu.c > @@ -231,6 +231,8 @@ static void kvm_cpu_instance_init(CPUState *cs) > kvm_cpu_max_instance_init(cpu); > } > > + cpu->lbr_fmt = -1; > + > kvm_cpu_xsave_init(); > } >
Reviewed-by: Dapeng Mi <[email protected]>
