SSBS Speculative Store Bypass Safe when FEAT_SSBS2 is implemented and FEAT_AA64 is implemented Allows access to the Speculative Store Bypass Safe bit. PSTATE SSBS is a 64-bit register. 63 13 63:13 Reserved, RES0. SSBS 12 12 12 Speculative Store Bypass Safe. Prohibits speculative loads or stores which might practically allow a cache timing side channel. A speculative value in a register is used in a potentially speculatively exploitable manner if it is used to form an address, generate condition codes, or generate SVE predicate values to be used by other instructions in the speculative sequence or if the execution timing of any other instructions in the speculative sequence is a function of the data loaded under speculation. The value of this bit is set to the value in the SCTLR_ELx.DSSBS field on taking an exception to ELx. 0b0 Hardware is not permitted to use speculative register values in a potentially speculatively exploitable manner if the speculative read that loads the register is from earlier in the coherence order than the entry generated by the latest store to that location using the same virtual address as the load instruction. 0b1 When the value of PSTATE.SSBS is 1, hardware is permitted to use speculative register values in a potentially speculatively exploitable manner if the speculative read that loads the register is from earlier in the coherence order than the entry generated by the latest store to that location using the same virtual address as the load instruction. ID 11 0 11:0 Reserved, RES0. MRS <Xt>, SSBS if !(IsFeatureImplemented(FEAT_SSBS2) && IsFeatureImplemented(FEAT_AA64)) then Undefined(); elsif PSTATE.EL == EL0 then X{64}(t) = Zeros{51} :: PSTATE.SSBS :: Zeros{12}; elsif PSTATE.EL == EL1 then X{64}(t) = Zeros{51} :: PSTATE.SSBS :: Zeros{12}; elsif PSTATE.EL == EL2 then X{64}(t) = Zeros{51} :: PSTATE.SSBS :: Zeros{12}; elsif PSTATE.EL == EL3 then X{64}(t) = Zeros{51} :: PSTATE.SSBS :: Zeros{12}; end; MSR SSBS, <Xt> if !(IsFeatureImplemented(FEAT_SSBS2) && IsFeatureImplemented(FEAT_AA64)) then Undefined(); elsif PSTATE.EL == EL0 then PSTATE.SSBS = X{64}(t)[12]; elsif PSTATE.EL == EL1 then PSTATE.SSBS = X{64}(t)[12]; elsif PSTATE.EL == EL2 then PSTATE.SSBS = X{64}(t)[12]; elsif PSTATE.EL == EL3 then PSTATE.SSBS = X{64}(t)[12]; end; MSR SSBS, #<imm> 2026-03-26 20:27:25 2026-03_rel