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Allow > the caller to select the potentially faulting variant by passing NULL > for the error pointer. Maybe make this "the sole caller" or some such? Because if there were multiple, they might easily disagree on what the best meaning of passing NULL is. > --- a/arch/x86/xen/pmu.c > +++ b/arch/x86/xen/pmu.c > @@ -293,22 +293,24 @@ static bool xen_amd_pmu_emulate(unsigned int msr, u64 *val, bool is_read) > bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err) > { > if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { > - if (is_amd_pmu_msr(msr)) { > - if (!xen_amd_pmu_emulate(msr, val, 1)) > - *val = native_read_msr_safe(msr, err); > - return true; > + if (!is_amd_pmu_msr(msr)) > + return false; > + if (!xen_amd_pmu_emulate(msr, val, 1)) { > + *val = err ? native_read_msr_safe(msr, err) > + : native_read_msr(msr); > } > + return true; Minor remark: Fold this and ... > } else { > int type, index; > > - if (is_intel_pmu_msr(msr, &type, &index)) { > - if (!xen_intel_pmu_emulate(msr, val, type, index, 1)) > - *val = native_read_msr_safe(msr, err); > - return true; > + if (!is_intel_pmu_msr(msr, &type, &index)) > + return false; > + if (!xen_intel_pmu_emulate(msr, val, type, index, 1)) { > + *val = err ? native_read_msr_safe(msr, err) > + : native_read_msr(msr); > } > + return true; ... this by moving them ... > } > - > - return false; > } ... above here? You might even de-duplicate the native_read_msr{,_safe}() invocations by moving them out of the if/else ... Jan