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sameo/kvm-msr-cpuid.md

Created March 2, 2021 15:14
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kvm-msr-cpuid.md

MSRs

3 MSRs array:

  • msrs_to_save reflects the capabilities of the host cpu, built on top of the constant msrs_to_save_all array.
  • emulated_msrs MSRs that are kvm-specific are put in emulated_msrs_all; filtering of emulated_msrs may depend on host virtualization features rather than host cpu features.
  • msr_based_features List of msr numbers which are used to expose MSR-based features that can be used by a hypervisor to validate requested CPU features. Built as a filter on top of msr_based_features_all

KVM_GET_MSR_INDEX_LIST

KVM_GET_MSR_INDEX_LIST returns the guest msrs that are supported.  The list
varies by kvm version and host processor, but does not change otherwise.

msr_list.nmsrs = num_msrs_to_save + num_emulated_msrs;

		if (copy_to_user(user_msr_list->indices, &msrs_to_save,
				 num_msrs_to_save * sizeof(u32)))
			goto out;
		if (copy_to_user(user_msr_list->indices + num_msrs_to_save,
				 &emulated_msrs,
				 num_emulated_msrs * sizeof(u32)))
			goto out;

CPUID

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