Paolo Bonzini wrote on 2014-08-01: > Il 01/08/2014 02:57, Zhang, Yang Z ha scritto: >>> TPR_THRESHOLD will be likely written as zero, but the processor >>> will never use it anyway. It's just a small optimization because >>> nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW) will almost always > be true. >> >> Theoretically, you are right. But we should not expect all VMMs >> follow it. It is not worth to violate the SDM just for saving two or >> three instructions' cost. > > Yes, you do need an "if (cpu_has_vmx_tpr_shadow())" around the > vmcs_write32. But still, checking nested_cpu_has is not strictly necessary. > Right now they both are a single AND, but I have plans to change all > of the > cpu_has_*() checks to static keys.
See v2 patch. It isn't a problem anymore. > > Paolo Best regards, Yang -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
