Check for AMD RDRAND bug #43
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newpavlov
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Jun 28, 2019
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Pre-Ryzen AMD CPUs have a very serious bug where they will sometimes give
0xFFFFFFFFas the output of RDRAND without setting the carry flag. This issue usually occurs when those CPU's awake from sleep: systemd/systemd#11810 (comment)This CL simply implement's systemd's fix, where they check for the bogus value and issue an error.
This PR also cleans up the
target_featurechecks. As we already fail to compile onsgxwhenrdrandis not enabled, theis_rdrand_supportedfunction checks can just betarget_feature = "rdrand".