On July 14, 2022 7:52:35 PM UTC, Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx> wrote: >Branch History Injection (BHI) attacks can be mitigated using the >BHI_DIS_S indirect predictor control bit located in MSR_IA32_SPEC_CTRL >register. Set BHI_DIS in MSR_IA32_SPC_CTRL to prevent predicted >targets of indirect branches executed in CPL0, CPL1, or CPL2 from >being selected based on branch history from branches executed in CPL3. >Support for this feature is enumerated by CPUID.7.2.EDX[BHI_CTRL] (bit 4). > >Users wanting BHI protection can specify spectre_v2=eibrs,bhi_dis to >enable hardware BHI protections. On platforms where BHI protections >are not available in the hardware revert to eibrs,retpoline >mitigations. Why is this a separately selectable option and not automatically enabled? -- Sent from a small device: formatting sux and brevity is inevitable.
