| Date | Wed, 20 Oct 2021 17:07:53 -0700 | From | Alexei Starovoitov <> | Subject | Re: [PATCH v2 14/14] bpf,x86: Respect X86_FEATURE_RETPOLINE* |
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On Wed, Oct 20, 2021 at 12:44:56PM +0200, Peter Zijlstra wrote: > + > + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD)) { > + EMIT_LFENCE(); > + EMIT2(0xFF, 0xE0 + reg); > + } else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) { > + emit_jump(&prog, reg_thunk[reg], ip); > + } else
One more question. What's a deal with AMD? I thought the retpoline is effective on it as well. lfence is an optimization or retpoline turned out to be not enough in some cases?
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