US 12,236,243 B2
Apparatuses and methods for speculative execution side channel mitigation
Jason W. Brandt, Austin, TX (US); Deepak K. Gupta, Portland, OR (US); Rodrigo Branco, Hillsboro, OR (US); Joseph Nuzman, Haifa (IL); Robert S. Chappell, Portland, OR (US); Sergiu Ghetie, Hillsboro, OR (US); Wojciech Powiertowski, Beaverton, OR (US); Jared W. Stark, IV, Portland, OR (US); Ariel Sabba, Lavon (IL); Scott J. Cape, Portland, OR (US); Hisham Shafi, San Jose, CA (US); Lihu Rappoport, Haifa (IL); Yair Berger, Pardes-Hanna Karkur (IL); Scott P. Bobholz, Bolton, MA (US); Gilad Holzstein, Haifa (IL); Sagar V. Dalvi, Hillsboro, OR (US); and Yogesh Bijlani, Portland, OR (US)
Assigned to Intel Corporation, Santa Clara, CA (US)
Filed by Intel Corporation, Santa Clara, CA (US)
Filed on Apr. 24, 2023, as Appl. No. 18/138,591.
Application 18/138,591 is a continuation of application No. 16/177,028, filed on Oct. 31, 2018, granted, now 11,635,965, issued on Apr. 25, 2023.
Prior Publication US 2023/0342156 A1, Oct. 26, 2023
Int. Cl. G06F 9/38 (2018.01); G06F 9/30 (2018.01)
CPC G06F 9/3844 (2013.01) [G06F 9/30101 (2013.01); G06F 9/3806 (2013.01)] 28 Claims
OG exemplary drawing
 
1. An apparatus comprising:
a core;
a register to store a capability bit that when set to a value of one indicates the core supports an always-on mode for indirect branch restricted speculation;
a hardware branch predictor to predict a target instruction of an indirect branch instruction; and
a model specific register to store an indirect branch restricted speculation bit for the core that when set to a value of one causes the hardware branch predictor to enable the always-on mode, wherein the always-on mode prevents branches predicted in a less privileged predictor mode from influencing branch predictions for indirect branches in a more privileged predictor mode, and stays enabled unless the apparatus is rebooted; and wherein the capability bit when set to a value of zero indicates the hardware branch predictor is to support another indirect branch restricted speculation mode that does not stay enabled unless the apparatus is rebooted.