Continue Spectre v4 review: * x86/bugs: Provide boot parameters for the spec_store_bypass_disable mitigation -> skip, no change * x86/bugs/intel: Set proper CPU features and setup RDS -> skip, no change but note that we keep using ibrs_inuse() instead of the feature bit. * x86/bugs: Whitelist allowed SPEC_CTRL MSR values -> skip, no change * x86/bugs/AMD: Add support to disable RDS on Fam[15, 16, 17]h if requested -> skip, no change * x86/speculation: Create spec-ctrl.h to avoid include hell -> skip, no change * prctl: Add speculation control prctls -> skip, no change * x86/process: Optimize TIF checks in __switch_to_xtra() -> skip, no change * x86/process: Correct and optimize TIF_BLOCKSTEP switch -> pick, no change * x86/process: Optimize TIF_NOTSC switch -> pick, context * x86/process: Allow runtime control of Speculative Store Bypass -> skip, no change * x86/speculation: Add prctl for Speculative Store Bypass mitigation -> skip, no change * nospec: Allow getting/setting on non-current task -> skip, no change * proc: Provide details on speculation flaw mitigations -> skip, no change * seccomp: Enable speculation flaw mitigations -> skip, no change * prctl: Add force disable speculation -> skip, no change * seccomp: Use PR_SPEC_FORCE_DISABLE -> skip, no change * seccomp: Add filter flag to opt-out of SSB mitigation -> skip, no change * seccomp: Move speculation migitation control to arch code -> skip, no change * x86/speculation: Make "seccomp" the default mode for Speculative Store Bypass -> skip, no change * x86/bugs: Rename _RDS to _SSBD -> skip, no change * proc: Use underscores for SSBD in 'status' -> skip, no change * Documentation/spec_ctrl: Do some minor cleanups -> skip, no change * x86/bugs: Fix __ssb_select_mitigation() return type -> skip, no change * x86/bugs: Make cpu_show_common() static -> skip, no change * x86/bugs: Fix the parameters alignment and missing void -> skip, no change * x86/cpu: Make alternative_msr_write work for 32-bit code -> skip, no change * x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP -> skip, no change * x86/cpufeatures: Disentangle MSR_SPEC_CTRL enumeration from IBRS -> skip, no change * x86/cpufeatures: Disentangle SSBD enumeration -> skip, no change * x86/cpu/AMD: Fix erratum 1076 (CPB bit) -> pick and revert previous version The upstream commit does this by adding the Zen specific init function. * x86/cpufeatures: Add FEATURE_ZEN -> pick, partial The bit is already define in a previous patch. Likely needs proper revert sequence later. * x86/speculation: Handle HT correctly on AMD -> skip, no change * x86/bugs, KVM: Extend speculation control for VIRT_SPEC_CTRL -> skip, no change * x86/speculation: Add virtualized speculative store bypass disable support -> skip, no change * x86/speculation: Rework speculative_store_bypass_update() -> skip, no change * x86/bugs: Unify x86_spec_ctrl_{set_guest, restore_host} -> skip, no change * Expose x86_spec_ctrl_base directly -> skip, no change * x86/bugs: Remove x86_spec_ctrl_set() -> skip, no change * x86/bugs: Rework spec_ctrl base and mask logic -> skip, no change * x86/speculation, KVM: Implement support for VIRT_SPEC_CTRL/LS_CFG -> skip, no change * x86/bugs: Rename SSBD_NO to SSB_NO -> skip, no change * x86/xen: Add call of speculative_store_bypass_ht_init() to PV paths -> pick, no change * x86/cpu: Re-apply forced caps every time CPU caps are re-read -> pick, no change