Enable setting CPUID feature for guest VCPUs by wcwang · Pull Request #277 · intel/haxm (original) (raw)

So using this PR it is only possible to remove already supported features. Is this OK?

I totally agree with your opinion. In the earlier design of this PR, we would have set the features out of current supported scope. But we found that if user set any value, which feature has not been implemented by HAXM, and then it would result in regression. Just as the feature FEATURE(TSC_DEADLINE), I once asked you in my review comments for PR #271. We will attempt to extend the supported feature set in future after more verification. In future, probably we will separate the default feature set from the supported feature set. Then user can add or remove features by calling this IOCTL. Currently, it is OK to only remove supported features.

So far I understand these bits are cpuid_1_features_edx FEATURE(FXSR) and cpuid_1_features_ecx FEATURE(AESNI)/FEATURE(PCLMULQDQ). So these are already supported, no need to set something from usermode.

Yes, you are right. Actually, this feature requirement came before the FEATURE(PCLMULQDQ) was added. We intended to enable such features by calling this interface. Due to aforementioned reasons, we screened the unsupported features out in this version. We will consider improving the current framework to meet more requirements. Any of your further input will be important for us and your contribution will be welcome. Thanks.